Reiza Studios, a highly reputable PC racing simulator developer based in Brazil, already has the Senna licence: http://www.reizastudios.com/news/en/1/new-game-with-ayrton-senna/
They’re taking their time about it, mind, but their Stock Car, Truck and ’88 McLaren Honda F1 simulators are already actually pretty damn realistic, so are well worth a look.
Although personally, I am just raring to go on Assetto Corsa by Kunos, which will utterly destroy Gran Turismo and Forza in realism stakes: http://www.assettocorsa.net/en/
To get an idea of what Kunos can do, check out the realism on this old sim, netKar pro, now available for a ridiculous 4 euros, and probably runnable on any functioning PC: http://www.netkar-pro.com/main/
It’s a crying shame that even reputable F1 fanatics are so blinkered to ignore serious racing simulators. You should all check this one out and see what you’re missing. Although note that you’ll need a wheel and pedals to drive a car…