While I agree with the last paragraph, any discussion about hypothetical future cars is nothing but a guessing game. All that counts is whats on the ground today.
Don't be too sure who leapfrogs who given the new relationship between Audi, Lambo and Porsche. I suspect the future will not the same as today, though I have no idea what direction any of them may go.
Regardless, the V10 is one of the finest cars available today at any price. I wouldn't take two GTR's for a V10, and vastly prefer the V10 R8 to the 998TT in any guise. No future R8 will relegate the current V10 to average.
The only other car I care about is the 458 Italia, and want one as soon as I can get one, which may be a while, despite my begging. I am on the list though.
2008 Ferrari F430 Spider F1