They need to continue with the "red tape free" research/funding for the new vaccines focusing on the portions of the virus that don't mutate much (if at all) along with the nasal vaccines.  We are back to the "take 10 years" garbage we had before since "Operation Warp Speed" is officially over.  Otherwise, they'll just be chasing variants.  Good for pharma, of course, and bad for us.  This is partly why I just sort of stopped at three shots.  This current approach is unsustainable.
		
 
		
	 
To be clear, there are only so many potential vaccine targets. Any part of the virus can mutate, randomly, with selective pressure (as would occur after vaccine exposure) impacting the fitness of derivative mutants. Vaccine targets must be big enough and accessible to cells which trigger the immune response, and even then, different viral parts may be more or less immunogenic, partially due to their molecular composition. If the structure is critical for viral fitness  (ie. it can't replicate/infect if it changes much), that's even better.
For many reasons, surface spike proteins were the most logical target for first generation vaccines. That's not to say there aren't other potential sites, and it's certainly reasonable to expect future vaccines to be polyvalent (targeting multiple viral parts of one strain and/or the same part of multiple strains). But I don't think it's as simple as looking for portions that "don't mutate much". As we transition out of pandemic covid, I expect we'll see less major variants of concern, in part due to less virus around to mutate, and diminishing returns in viral fitness with subsequent mutants, as 
@Doug B alludes to above (the horse example).
And while I love the concept, the more I read about mucosal (nasal) vaccines, the less I think they're the answer. It will be interesting to see what next gen vaccines are ultimately developed.