Clearly the potential opposition to the F-35 think there must be something in this stealth idea, otherwise why develop PAK-FA and J-20?
Yes, stealth is currently a big differentiator, and commands a high price for being so. I have heard people opine that it will eventually become like previous differentiators, part of the base-line package. Detection technology will have moved on too, having to work harder to detect it, but why make it easy for them? That's the way weapons have evolved since Harold copped an unfortuneate one at Hastings, and probably long before that too.
What gnaws away at me about stealth, is the way that it imposes limitations on what would otherwise be more straightforward design matters, and it is a one-shot system. If it gets busted by a spotty kid in a attic with an IPod, two baked bean cans and a bit of string, this would seriously undermine it's credentials. We will have paid a huge price for the capability.
In my own simplistic way, I rationalise the airframe as being one of the (relatively) more standard parts of an airborne weapon, and lots of the differentiating bits being the wizardry that gets stuffed inside it or in the pods hanging under the wing. That way, longevity can be improved and even some of the very old-timers learn new tricks by upgrading that wizardry and glueing any structural airframe bits back together when they break (does my lack of technical expertise show?). When the airframe is also part of the wizardry, is that just as upgradeable?