While there is no committee sitting around setting standards for what qualifies as 'nth gen' and so forth, there are reasonable expectations on certain features that are either evolutionary or revolutionary via innovations based upon established technologies on previous fighters.
Low radar observability is one such expectation and I speculate that the '6th gen' fighter will have active cancellation at the surface level, nothing SPECTRA-like or 'plasma stealth', but far superior based on semiconductor devices manufacturing technology. What this mean is that all current fighters in USAF and USN inventory will be '6th gen' in this respect once this technology is installed.
Physical ammunition will be replaced...
The US Air Force Will Employ Lasers - Business Insider
The AESA radar will be sophisticated enough to produce real time imaging of targets that will rival B/W photos, enabling the pilot, remote or in-cockpit, to immediately ID his targets based upon their unique physical attributes, ie Su-whatever or MIG-whatever or J-20 or J-31, before going 'silent' again.
There will be no need for engines powerful enough to supercruise above Mach 2.5 but there will be a need for an engine powerful enough for a supersonic dash above Mach 2.5. We will have that. The engine will be more fuel efficient as well with the possibility of a new fuel formation. Thrust vectoring will standard with no need for 3D.
Avionics will be voice commanded.
Air dominance - The ability of an air force to compel other air forces to rearray themselves, usually into inferior postures.
Air superiority - The ability of an air force to achieve complete control, or reacquire complete control, of any airspace with statistically and tactically insignificant losses, if any.
Air supremacy - He flies, he dies.
We will either go from dominance to supremacy or if the enemy is foolish enough, we may have to stay in superiority for a short amount of time. But the US will continue to own any airspace at our convenience -- should we get pissed off enough to do so.