I'll try to keep my current Mk6 Golf GTI going as long as possible! The way gti prices is going up at present, it is getting a bit too close to nearly new high end BMW 3 series coupe and Merc C-class coupe. I think the Mk7 gti will easily cost more than £30000-£35000 with option and will depreciate even heavier!
For my sunday drive, I don't think I will ever sell my gen 2 911 c2s. It will be my last Porsche---They depreciate too much. The only sensible purchase is a low mileage second hand F430 to replace my F355 but I think the latter still looks great!