Already, 2019 is on track to become the year that some of the most valuable VC-backed companies smash records set during the height of the dot-com era. Four companies in particular — Lyft, Uber, Pinterest and Airbnb, also known as LUPA — dominate the headlines as the first high-profile deals of the mobile-app generation to go public.

"The question is, are these companies going public because they want to or because they have to?" said Henry Ward, CEO of equity management software company Carta. "I think in many cases, it's because they have to."

Ward reasons, "You will see a flip where the best companies, with the strongest founders, can control their fate and not go public. The weaker companies that can't control their fate will."

Lyft, now valued at roughly $20 billion, began trading on the Nasdaq Friday morning at $87.24 per share, 21 percent above its original IPO price of $72 per share. Uber filed confidentially with the SEC last December and is expected to list on the New York Stock Exchange this month with a reported valuation of $120 billion. Pinterest filed its S-1 in March with a private valuation of $12 billion and is also expected to make its public debut on the New York Stock Exchange this month. (Airbnb has not officially announced any IPO plans, but it has been reported recently that the accommodation-sharing site will issue shares directly to the public.)

In their latest VC rounds, all four LUPA companies, plus Peter Thiel-backed Palantir Technologies and Slack, have collectively raised a whopping $26 billion. In total, they bring a private valuation of $158 billion to Wall Street.

Amid the reports and reactions, big questions remain: What can we expect after these aging tech giants list as publicly traded companies? And what do these billion-dollar exits mean for the next crop of VC-backed start-ups?