For what is still a niche market, there sure are a lot of big hitters taking their shots at building the go-to phablet of choice. Though phablets haven't yet become the hot sellers many pundits expect, that hasn't stopped Apple (AAPL 0.36%), Samsung (NASDAQOTH: SSNLF) and other leading smartphone manufacturers from tossing their hats in the ring.

Apple's iPhone 6 Plus phablet has already hit the streets, though some pre-orders have been delayed. The Samsung Galaxy Note 4 is also available. If you've seen Samsung's commercials slamming Apple's new phablet, it's pretty clear the South Korean smartphone king sees the iPhone 6 Plus as its primary competitor. But if the rumors are true, and they've been circulating for some time, Google (GOOG 9.39%) (GOOGL 9.73%) is about ready to introduce its latest phablet, hot on the heels of its other large-screen smartphone, the Moto X.

Why all the fuss?
Because of their size -- generally considered to be devices with screens from 5 or 5.5 inches up to 7 inches – phablets have yet to catch on in a big way. But as more consumers weigh the costs and necessity of owning both a smartphone and a tablet, many industry insiders expect phablets will soon command a significant piece of the mobile market.

According to one estimate, phablets will outsell tablets by a whopping three-to-one in just four years. But tablet sales have been waning for some time now, so that's no real surprise. What might come as more of a shock to fans of handsets, be they Apple, Samsung, or Google-inspired devices, is that estimates suggest the number of phablets sold will also match those of "traditional" smartphones within a couple years. By 2019, phablets are expected to own nearly 60% of the overall smartphone market. That's heady stuff, and makes it pretty obvious why all the mobile big boys are diving headlong into phablets.

Google's foray
Google's Android OS absolutely dominates the smartphone market, and it's growing. For the first time ever, global smartphone sales surpassed 300 million units in 2014's second quarter, and nearly 85% of all those phones were running Google's operating system. As the No. 1 seller of smartphones on the planet, Samsung is to thank for much of Google's OS leadership position, as the two have worked side-by-side to bring smartphones to the world for some time now.

Should the rumor mill prove correct, Google has contracted with an independent manufacturer, in this case Motorola, to build its latest, greatest phablet. Just as it did with its smallish phablet, the 5.2-inch Moto X, Google outsources the building of its devices. Though not necessarily considered the top-of-the-line phablet alternative on the market, Google's Moto X has earned some solid reviews. But apparently, the Moto X didn't satisfy Google's interest in phablets, so get ready for "Shamu."

According to 9to5Google, a generally reliable source for information on all things Google, the OS king is set to debut a 5.92-inch phablet dubbed "Shamu," to compete directly with Apple's 5.5-inch iPhone 6 Plus, and Samsung's 5.7-inch Galaxy Note 4. With a rumored screen resolution of 2560 x 1440 and a top-drawer battery, Google's latest phablet should stack up well against Apple's and Samsung's newest devices. An ace up Google's sleeve is that current smartphone owners trading up to a phablet will likely look to an operating system they're familiar with, and Google owns 84.7% of that market worldwide.

Final Foolish thoughts
Though Apple's new iPhone 6 and 6 Plus smartphones have encountered a few hiccups -- including a cellular outage due to a flawed OS and durability concerns -- there's no denying they've enjoyed a successful introduction, including over 10 million units sold the first weekend. And Samsung's Galaxy Note 4, with its unique Gear virtual reality headset option, along with unparalleled distribution channels, can't be discounted.

But competing with Apple, or even its smartphone partner Samsung, is hardly enough to prevent Google from introducing a new phablet. Competition is nothing new for Google CEO Larry Page and team, and if the rumors prove correct, he's getting his ducks in a row for an all-out war with some of the biggest phablet players around. If Google has its way, and it often does, the phablet market is about to get a lot more interesting.