The trouble is that all the paradigms you mention come with a bigger price tag than the thing they replaced. So history suggests that X-37s, Auroras, hypersonic attack systems or sharks with laser beams on their heads are likely to cost more than a bog-standard F-35.
The other way of looking at it is that you can still do an awful lot if you intelligently operate an aircraft with maneuver, chaff, flares & EA. Wouldn't you be able to do the same things easier, or do much more, if you had a bit of stealth as one of your tools too?