When rumours of Gran Turismo 6 surfaced during PlayStation 4's reveal event, some questioned their legitimacy. "Look at the games coming out on the PlayStation 3," Sony Worldwide Studios VP Michael Denny supposedly said, "like The Last of Us, Beyond: Two Souls, GT6, and then on the third-party side of things another fantastic Assassin's Creed, GTA..."

It seemed an odd move. After all, why would Sony opt to release the next edition of a game viewed by many as the company's greatest graphical showpiece on eight-year old hardware, rather than add another string to PS4's bow?

Nevertheless, the rumours turned out to be true. Yesterday, Sony announced Gran Turismo 6 for release on PS3 this Christmas, albeit it alongside the suggestion from series creator Kazunori Yamauchi that the game could eventually work its way onto PS4, too.

But why did Sony stick to current-gen tech for the initial release of GT6, rather than wheel Polyphony straight onto PS4? Well, while the answer isn't yet clear, the cost of Gran Turismo's R&D, the risk to other investments, and the temptation for consumers to double-dip (i.e. purchase the same game twice on multiple formats) are likely the most influential factors.

Gran Turismo 5 took far longer to create than Sony had initially planned for - the game was originally announced at E3 2006, and suffered multiple delays until its eventual release in November 2010. An extended development schedule, of course, means expanded budgets, and Gran Turismo's development probably didn't come cheap. From bespoke engine creation to meticulous gameplay tweaks and extensive marketing campaigns, the costs associated with Gran Turismo are likely amongst the very top tier of development budgets.

But as one of Sony's 'evergreen' titles - a game that continues to sell throughout the life of the console - the money is worth it. Gran Turismo 5 continues to perform well, with latest sales figures standing at 10m units sold worldwide, but the (likely) inflated costs of its creation would suggest a profit margin lower than that typically associated with a title of such calibre.

From a business perspective, then, releasing another Gran Turismo title that shares tech with a previous release would clearly seem the more attractive decision for Sony, who could maximise returns on its previous investment, and give Polyphony the necessary time to create a worthy next-gen title for release during that vital second or third year.

Then there's DriveClub to consider - the new next-gen racing IP from MotorStorm creators Evolution Studios. Releasing GT6 alongside DriveClub would have severe implications for Evolution's game, cannibalising sales as players plump for the more established 'premier' racing IP. And while it's unlikely that Sony expects DriveClub to perform anywhere near as well as GT at retail, it wouldn't make sense for Sony to invest in a property that would be immediately overshadowed by another one of its own.

In fact, the greatest surprise from Gran Turismo 6's announcement wasn't the fact that Gran Turismo 6 will start life as a PS3 game, but that it isn't coming to PlayStation Vita either. Sony desperately needs a AAA release to spur on the performance of its struggling handheld and a portable version of Gran Turismo 6 could have gone some way to recoup flagging sales. It hasn't been ruled out for the future, of course, but Sony needs something quick, and it's unlikely that games like Tearaway and Killzone: Mercenary will convince consumers to lay down the cash on a Vita this Christmas when it could be put towards a PS4.

Still, releasing GT6 on PS3 at this stage of the console's life cycle is a welcoming show of support for Sony's ageing platform. Without any major first-party titles left in the pipe for Xbox 360, Microsoft's focus has clearly moved to next-gen, while Sony's 10-year plan for PS3 gradually comes into fruition. And if Sony can bundle Gran Turismo 6 with PS3 this Christmas as a low-cost alternative to next-gen consoles (which will surely be difficult to find themselves) it could position itself well in the low-end hardware market, and shift inventory it may have otherwise struggled to move next year.

So what does the future hold for Gran Turismo beyond GT6? Well, a PS4 release is almost certain - Yamauchi has said as much. But despite his comments, whether it arrives as the game unveiled yesterday is still up for discussion. Based on Sony's comments that Gran Turismo 6 will place a greater emphasis on long-term monetisation via DLC and the industry's ongoing intention to deliver games as services rather than a one-off product, the firm appears to be making the first steps towards turning the racing franchise into a platform. And with a connected future ahead, releasing a platform where users can fully customise their racing experience and extend the longevity through downloadable content seems an exciting inevitability - and a worthy investment for PS4.