As a point of discussion, with all this talk of design compromises, becoming a white elephant, or the next Defiant- it is interesting to note there have been aircraft with some significant compromises that had long careers. "Gimmickry", design compromise and performance in some aspects less than the aircraft it is replacing (or contemporary designs) does not automatically equate to failure. Some have been game changers.
I offer:
The Harrier, first generation- A very compromised design, all revolving around the V/STOL requirement. Slow, poor visibility, poor load when compared to contemporaries. Had a long, successful career.
A-7 Corsair. Bucked the trend of 1960's faster is better. The SLUF served as a capable, under sung aircraft.
MRCA/Tornado. RAF was looking for a Vulcan and Buccaneer replacement. Did not have nearly the range or payload capability of either. Used the swing wing to meet requirements, which complicated the aircraft, and was/is seen as gimmickry by some. Has had a long career with some success. The "best" intruder ever? I'll leave that alone.
Phantom. Designed for fleet defense. Gimmickry all missile design as guns were considered obsolete. Compromised dog-fighter. Lack of guns was later proven wrong and the plane was adapted in later versions. Major upgrades and multiple versions and multiple roles. Successful by any measure. Perhaps the F-35 will mature like this?
Tornado IDS. Replacement for the Lightning and Phantom. Performance less than those (yes I understand it was not intended to be a dog fighter). Mid range career, of debatable success. Best interceptor ever? Probably not.
F-18F Super Hornet. Replacement for the F-14 in Fleet Defense. Less performance than the Tomcat in most aspects, but seems to be doing just fine. Granted less sexy.
F-104. Majorly compromised design, with high speed trumping all else. Had a long career, good orders (yes cries of bribery I know) and adopted to other roles. "Best" fighter? No. "Best" nuke delivery? No. "Best" maritime strike? No.
For every Defiant, Buffalo, XB-70, Cutlass, B-58 etc, there have been others with serious compromises in design and performance than have served just fine- I think it is way too early to profess the obsolescence of the F-35