DC as a state is unacceptable.
Putting DC in Virginia wouldn’t make any sense since it came from Maryland (the VA part was already returned). It would also seriously mess up a key state.
Giving it back to Maryland would make sense but that would take what is already a very very difficult state for Republicans and put it totally out of reach.
The best solution comes from Auh2orepublican, take the DC suburbs in MD and VA and join them with the District in a new state. It would be safe rat but VA would be made pretty much safe Republican and Maryland would become a swing state.
That will never happen because it requires too much effort and imagination for our gray-suited overlords and MD and VA won’t want to lose tax dollars.
Either the situation in DC will remain the same forever or it will be given a vote in the House (but not the Senate) by constitutional amendment, or given the vote by law (which would be unconstitutional and overturned). The latter happening might be necessary to precipitate the former.
Retrocession to Maryland would be a long term possibly also if Maryland would take them.
Puerto Rico needs to be studied to discern how it would vote if made a state (the conventional wisdom of “heavily rat” is disputed by Puerto Rican freepers.)
The other territories are far too small to ever be states.
Of course DC voting rights and the status of Puerto Rico are on almost nobody’s priority list
Other than PR, the other territories are, as you said, far too small to become states, but they could be attached to existing states, such as, e.g., adding Guam and the Northern Mariana Islands (and the Midway Islands and other lightly inhabited or uninhabited islands in the northern Pacific) to the State of Hawaii, which would make the state less Democrat.