Tech investors have laughed all the way to the bank in 2019, as evident from the NASDAQ 100 Technology Sector index's impressive gains. But not all tech stocks have managed to create wealth for investors despite starting 2019 on the front foot. Xilinx (NASDAQ:XLNX), Twilio (NYSE:TWLO), and Glu Mobile (NASDAQ:GLUU) shareholders would have expected market-beating performances, but that didn't happen. The initial promise shown by these stocks eventually faded away.

XLNX Chart

XLNX data by YCharts

However, don't be surprised to see all three companies stage a strong comeback in 2020 and turn into top growth stocks. Let me explain why.

1. Xilinx could re-create its old magic

Xilinx was a hot growth stock at the beginning of 2019. The deployment of 5G (fifth-generation) wireless networks gave the chipmaker a nice shot in the arm, helping it deliver rapid top- and bottom-line growth. But adversity soon struck thanks to the U.S.-China trade war.

Xilinx couldn't sell its products anymore to Huawei, which has been playing a critical role in 5G deployments in China. At the same time, the company saw a cool-down in 5G deployments as customers started transitioning to custom chips made specifically for 5G applications from the field-programmable gate arrays (FPGAs) that Xilinx makes.

Hand drawing positive stock chart return

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However, the chipmaker remains confident that 5G will continue to remain a catalyst for Xilinx in the long run. And don't be surprised to see Xilinx's 5G catalyst step up big-time in 2020, as telecom operators are expected to spend a lot more money on related wireless infrastructure next year.

According to Gartner's estimates, worldwide 5G wireless network infrastructure revenue is expected to hit nearly $4.2 billion in 2020, significantly higher than 2019's estimated revenue of $2.2 billion.

What's more, 5G infrastructure spending will likely continue to rise at a rapid pace in 2021 and hit $6.8 billion. This massive jump in 5G infrastructure spending will be driven by network rollouts in more regions such as Germany, Canada, France, Spain, the Middle East, and others. In 2019, 5G deployments have primarily happened in South Korea, Japan, and the U.S.

So, 2020 might be the year when 5G network deployment gains critical mass and open up a bigger market for Xilinx. This could give the chipmaker's financials a nice bump, as 38% of its revenue comes from the wireless business that recorded terrific annual growth of 24% in the last reported quarter. 5G rollout in newer markets will spur demand for Xilinx's programmable chips and help the company infuse some momentum into its top- and bottom-line growth once again.

2. Twilio's short-term troubles won't last long

Twilio was my top growth pick for 2019. The cloud communications specialist looked all set to build upon 2018's terrific rally, as it was clocking rapid growth. The good news is that the cloud communications specialist has sustained its impressive growth rate this year, but that hasn't been enough to satisfy the market's expectations.

Meanwhile, Twilio's management gave investors another shock recently when it downgraded its fiscal 2019 earnings guidance thanks to what it calls a calculation error. All of this seems to have dented investor confidence in Twilio, but savvy investors should capitalize on the stock's recent decline.

That's because Twilio's growth won't be slowing down anytime soon. The company projects $1.15 billion in revenue in fiscal 2019, an increase of 71% over 2018. For comparison, Twilio had clocked 63% revenue growth in 2018, meaning that the company has switched up a gear thanks to the acquisition of email marketing player SendGrid that was completed in January 2019.

SendGrid has added 84,000 new customers to Twilio's client base. This gives Twilio a nice head start into the email marketing business that's growing at almost 20% a year, according to Transparency Market Research. Concurrently, Twilio has a new product to sell to its organic customer base and vice versa.

So, the synergies of the SendGrid acquisition have the potential to help Twilio sustain its impressive pace of growth in the new year. Elsewhere, Twilio's core business of providing a cloud communications platform will be yet another growth driver.

Twilio is primarily known for being the middleman that delivers push notifications, messages, voice calls, videos, and other content to users within apps such as Netflix, Lyft, Airbnb, and others. This is a fast-growing space that's expected to clock an annual growth rate of 26% through 2023, according to a third-party estimate.

In the end, it can be concluded that Twilio is plying its trade in markets that are growing at an impressive pace. So don't be surprised to see Twilio become a growth stock next year, since it has enough catalysts to overcome its recent troubles.

3. Glu is already in turnaround mode

After sizzling on the stock market in 2018, Glu Mobile was tepid this year. The mobile gaming specialist got off to a promising start, but that was derailed by one bad quarter. Investors panicked and sold Glu stock once the company substantially downgraded its full-year bookings guidance.

The problem with Glu was that one of its games failed to take off -- WWE Universe didn't do as well as the company expected. But it didn't take long for Glu to regain its momentum. Glu's third-quarter report revealed a record bookings figure that was higher than what the company had originally estimated.

The improved performance was driven by Glu's strategy of shifting its focus toward other games once it realized that WWE Universe was not gaining enough traction. Glu's diversified list of games helped it make a quick comeback.

Glu has lined up more games for next year -- Disney Sorcerer's Arena, Originals, and Deer Hunter Next. However, the company has clarified that it expects low-single-digit growth in revenue next year irrespective of how these titles perform. The company has the potential to deliver much stronger growth assuming these titles click.

Additionally, Glu Mobile is capable of delivering profitable growth next year thanks to its "platform game" strategy. According to Glu, platform games are those that are capable of generating long-term revenue with minimal investments. Diner DASH Adventures is the latest example of such a title that helped improve its margins.

GLUU Gross Profit Margin (TTM) Chart

GLUU Gross Profit Margin (TTM) data by YCharts

Glu has decided to reduce its outlay on this game thanks to its strong customer retention and engagement. Platform games are why the company's gross profit margin jumped 3.5 percentage points last quarter. As Glu looks to develop more titles that could deliver sustainable growth, its profitability should also improve.

Don't be surprised to see a stronger earnings performance from Glu Mobile in 2020, which might be enough to turn it into a growth stock once again.