Like other major video-game publishers, Take-Two Interactive (NASDAQ:TTWO) is benefiting from selling games directly to consumers through digital downloads, but even that tailwind pales in comparison with the company's biggest performance driver. That's not to downplay the significance of the digital sales transition, but the publisher's high-flying stock run in recent years has even more to do with the ongoing success of Grand Theft Auto V.

Take-Two's shares are up more than 800% over the past five years and trade at a whopping 43 times forward earnings estimates. However, its forward price-to-earnings-growth ratio is just 0.2, so the stock actually looks cheap if the company can continue deliver impressive earnings gains. Much of that will come down to how much gas the Grand Theft Auto series has left in the tank.

Three people on motorcycles sailing through the air over a bridge in "Grand Theft Auto V".

Image source: Take-Two Interactive. 

GTA V still has big sales potential

According to the NPD Group's tracking, Grand Theft Auto V came in as America's second best-selling game in August, trailing only Madden NFL 18 from rival publisher Electronic Arts. Of course, it's worth noting that EA's football game released last month, while the first versions of Grand Theft Auto V landed on store shelves all the way back in September 2013. Across its incredible run, Take-Two's monster hit has shipped over 80 million copies, made America's top 10 best-selling-games list in 41 out of its 49 months on the market, and delivered the best overall revenue and unit sales in the history of NPD Group's industry tracking. The game's online mode is also a hit that's generating substantial in-game content sales that are hugely profitable. 

Based on numbers from SteamCharts, which tracks engagement on the PC gaming platform Steam, the average daily concurrent players for GTA V from June to August of this year increased roughly 41% over the prior year period, and it's probably safe to assume that engagement is up on PlayStation and Xbox platforms as well. With an expanding sales imprint, evidence that the game is still making substantial gains in its active player base, and the company's regular introduction of new content, there's a strong chance that GTA V's online mode will continue to deliver year-over-year sales increases.

There's also the possibility that Take-Two will release the game on Nintendo's (NASDAQOTH:NTDOY) Switch console -- potentially leading to another dramatic sales bump. Nintendo platforms typically attract a younger user base, but with news that M-rated games including Doom and Wolfenstein II: The New Colossus are heading to the system, it's clear that publishers are interested in testing the market for games intended for older audiences on the platform. Take-Two could likely generate millions of additional GTA V sales if it releases the game on Switch.

All told, I think it's feasible that total lifetime shipments for Grand Theft Auto V will exceed 100 million units. 

A car from "Grand Theft Auto V".

Image source: Take-Two Interactive.

Will the next GTA games be as successful?

Grand Theft Auto V is one of the most profitable games in history, which makes delivering a more successful follow-up a tall order, but the franchise still has growth potential ahead.

The smart move for Take-Two, and one it is likely to pursue for the series' next installment, is to replicate the release schedule that helped make GTA V such a big hit. That means launching the next GTA sequel on PlayStation 4 and Xbox One when these systems are near the tail end of their life cycles to take advantage of their large user bases -- and then delivering an updated version of the game for next-gen platforms and PC at a later date to benefit from new hardware momentum and players who are willing to purchase the game again to experience an updated, graphically superior version.

The franchise actually has considerable room for growth in the digital sales space. Following the incredible success of GTA V's online mode, it's likely that Take-Two will put an even greater emphasis on creating a multiplayer mode that keeps players engaged (and spending) with the series' next installment. As one of the most powerful brands in gaming, the series also has the potential for a much bigger presence in mobile. Take-Two already sells older series entries for smartphone and tablet devices (Grand Theft Auto: San Andreas retails at $6.99 and is currently the ninth best-selling paid game in the iOS store), but it has yet to release a franchise installment that's built from the ground up to take advantage of the unique benefits these platforms offer.

Take-Two is building its franchise portfolio

The Grand Theft Auto series appears to be in strong shape. Each mainline entry has outsold its immediate predecessor, and even if the next installment doesn't manage to match GTA V's incredible unit sales, it could still be more profitable thanks to growth for game downloads and in-game content sales. However, Take-Two still needs to continue building its portfolio of other hit franchises, and it seems to be making progress on that front. In addition to its annual sports releases, the company is now aiming to debut at least one new, blockbuster title each year -- with a new entry in the Red Dead Redemption series launching in spring 2018 and at least one other high-profile, non-sports title due for release next year fiscal year.

With Grand Theft Auto looking as if it will continue to be a powerhouse franchise, an expanding lineup of other viable properties, and industry tailwinds at its back, I think Take-Two stock still has room for big growth.

Keith Noonan owns shares of Take-Two Interactive Software. The Motley Fool owns shares of and recommends Take-Two Interactive Software. The Motley Fool recommends Electronic Arts. The Motley Fool has a disclosure policy.