I've been a big proponent of DC statehood for some time now. And one thing I really like about it as a political play is that it is (a) morally correct (obviously DC residents should have representation in Congress), (b) politically advantageous (it's two safe Democratic seats), and (c) immune from direct retaliation. You're usually lucky to get even two, let alone all three. Compare court packing: it'd be politically advantageous for Democrats to add more justices to the Supreme Court, and it's perhaps arguably morally justified, but it's also easily open to retaliation -- the next time the GOP controls Congress, they'll just add even more seats to re-pack the judiciary.
But DC statehood is relatively immune to that sort of tit-for-tat. I can imagine the conversation:
"You're only adding DC as a state to secure two new Democratic senators! Well if you do that, the next time we're in power we'll add two new states with safe Republican majorities!""Oh? Are there non-state territories under permanent American dominion that are overwhelming made up of conservative White people?"
"Yeah. Funny, that."