Right now 5 AL teams are already toast (BAL, KC, TOR, DET & SEA) and it is my opinion, the White Sox and Angels will be sellers by July. There's even a chance one from the Guardians, Rangers or A's might be sellers. (The Guardians have been shopping SP'ers even as they compete.)
In the NL, things look pretty bunched up near the last WC slot, but IMOthe Cubs and Phillies will likely have a solid lead on many teams still "in it" now. Miami and SF are all but dead now. Add Cincy, Pitt & WSH and that's 5. That makes 10 MLB teams out of it by mid June. Add CWS, LAA, NYM and SD, and we're up to 14- almost half the teams. Add the Guardians, who are already looking to sell and maybe 1-3 teams from AZ, COL, TX & OAK, and we should see over half the teams as seellers by the end of July.