Yes - Everybody should compete to their fullest cabability at every event they attend. Nothing more to be said here.
No - FIRST did not (probably could not) keep the number of teams making "last minute" travel arrangements small.
You are probably correct in guessing that many of the teams that win regionals/awards this year will already have qualified some other way. But, it does not seem likely that FIRST will let the vacant slots created by the "overqualified" teams remain vacant. Those spots will probably be filled from a wait list of even teams or a wait list of Regional runners up (or both).
I would guess that by the time registration closes in December, there will be somewhere in the neighborhood of 177

teams registered. This is not an "overwhelming majority" of the 288 teams that FIRST/Disney is expecting. Over 100 teams will have to finalize their travel plans on relatively short notice. I hope that they can figure out how to do it, or the Championship will be a lot smaller than we expect.
P.J.