Predicting the next stock market bubble is a completely inexact science. No one knows when a bubble will pop -- but what we do know is there's practically a 100% chance that some sort of crash will occur at some point, because history points us to this fact, just as there's a nearly 100% chance that stocks will come roaring back following that crash.

Today, rather than pinpoint a specific time of when a bubble might occur, I'm going to pull out my proverbial crystal ball and project what I believe could be the next three bubbles to burst. Again, these are pure speculation on my part and not a doomsday call, so keep that in mind.

Source: Urbanicsgroup, Flickr.

China's real estate market
As someone who has argued against using real estate as a primary investment opportunity, I see no potentially greater threat out there than China's real estate bubble.

Since 1998, China's real estate values have risen by more than 200%, with only a single year registering a decline (2008). October alone demonstrated year-over-year home price appreciation of 10.5%! The allure of housing in the rapidly growing emerging-market country is that it has provided, at least over the past five years, a considerably better return than the stock market, which has returned only a 6% gain over the same period. According to Standard Chartered estimates via Bloomberg, China's urban residential market value as of the end of 2012 was worth $18.9 trillion compared with its stock market and bond market, which were worth $3.8 trillion and $4.3 trillion, respectively.

What's more, Standard Chartered notes that real estate has made up more than 60% of investment assets held by Chinese citizens since 2008, compared with just 26% in the United States -- and we saw what happened to those U.S. citizens that relied on housing investments to drive their growth. And it wasn't pretty!

If there's one aspect of inflation that I believe the Chinese government fears more than anything, it's housing inflation, having seen what happened to its competing economic superpower, the United States, in 2009. China has already pushed through efforts to stem housing price inflation by raising interest rates and limiting home purchases, but it hasn't had a huge effect with smaller suburbs outside of larger China metros not abiding by these laws, since they haven't been privy to nearly the same price appreciation as their larger metro counterparts.

At some point, this exponential growth in housing is going to cease, and that makes me worry for companies like E-House (NYSE: EJ) which provide real estate information services and consulting within China. E-House's recent rally is based purely on home price inflation and housing investments and very little on the underlying improvement in genuine first-time housing demand. That has all the makings of a potential bubble.

The U.S. IPO market
This has been the busiest year for initial public offerings, or IPOs, since the financial crisis hit, with 139 companies going public year to date through Friday. This year alone, 23% of those offerings have priced well above their initial IPO range, with an average first day of trading gain ranging from a low of 13.6% in April (yeah, that's the low!) to a high of 32.3% in February, as you can see in this chart from The Wall Street Journal:

Average first-day trading gain for U.S. IPOs in 2013 by month. Source: The Wall Street Journal.

Normally, a hot IPO market is a direct result of a strong market and robust economic times. However, the sheer number of IPOs hitting the market this year is making it difficult on individual and institutional investors to keep up on exactly what these companies do and how they make money. In other words, the market is overwhelmed and oversaturated with new issues, and that's not a good thing.

Perhaps no IPO made a bigger splash than Twitter (NYSE:TWTR) earlier this month, which surged 73% on its first day of trading to a market valuation of roughly $25 billion. At this valuation, Twitter is worth approximately 22 times its 2014 sales projections, which is double that of both of its social-media peers Facebook and LinkedIn, which have both proved their ability to Wall Street that they can turn a healthy profit, unlike Twitter. Is Twitter really worth that much more of a premium than its social-media peers? I'm not so sure about that.

The biotech industry is another stomping ground for a mind-boggling number of cash-raising IPOs. One thing you have to understand about biotech IPOs is that they're often undertaken by companies with a promising drug candidate or two that's in early to mid-stage studies. Because these trials are costly, these companies often choose to go public to raise some much-needed cash to run their clinical trials. With a relatively low success rate of bringing drugs from the laboratory setting to pharmacy shelves in the first place, the odds are often stacked against these IPOs -- yet many new biotech IPOs remain oversubscribed.

The pace at which IPOs are coming to market and their initial first-day pop just doesn't seem sustainable, all things considered, and it could be a bubble that's ready to burst.

The U.S. auto-loan market
I have to give all credit here to fellow Fool Rich Duprey, who alerted us to the potential for a problem in the U.S. auto sales market back in May. After a bit of personal digging, I would certainly suggest that there could be some merit to the idea that the car-loan bubble is about to burst.

The most recent auto-loan delinquency rates for the third quarter, which are compiled by Experian, look relatively benign on the surface, but if you drive a bit deeper you'll find some potentially worrisome statistics.

On the surface, outstanding automotive loans reached a new record of $782.9 billion, up $103 billion from the third quarter last year and by far the highest loan balance since Experian began keeping these quarterly records seven years ago. Thirty-day loan delinquencies fell 9 basis points to 2.58% from the year-ago period.

"So what's the problem?" you might be wondering. The problem is that loans in the nonprime, subprime, and deep-subprime segments continue to rise. In the latest quarterly tally, 36% of all loans written were to people with questionable credit, up from 35.9% in the year-ago period. Up until now, these nonprime lenders haven't had an issue paying their car loans, but I'd also attribute that to the continued expansiveness of the U.S. stock market and economy. What happens if the stock market stalls or GDP growth falls below 2%?

As the proof in the pudding, we've seen banks creeping into the subprime space again in an effort to reach poor credit customers wanting to buy a car. According to Standard & Poor's, the average loan-to-value ratio on vehicle sales to consumers who have less than prime credit right now is 114.5, up from 112 a year ago, and closing in on the 121 peak before the financial crisis. If anything, perhaps this shows that banks and consumers didn't learn their lesson the first time around. I'd consider this a possible bubble worth keeping your eyes on.