Well, if you have to replace the rear wheel anyway, get an 8/9/10-speed one and spread the frame or struggle slightly during wheel changes. It's not that bad. Of course, if you go to 9 or 10-speed you will need new shifters, a new chain and possibly a new front derailleur.

If you want to keep it 7-speed, get an 8/9/10-speed wheel anyway and the 4.5 mm spacer needed with a 7-speed cassette.