MI looks overwhelmingly likely to be a fresh Republican set of maps and it's really difficult to imagine a new PA map that's not more favorable to Republicans. CA should be mostly status quo, and the seat getting cut is almost certainly Lowenthal's. (Garcia could be screwed by redistricting, but then again so could Levin). NY and IL will see harder gerrymanders but that adds up to way fewer seats than FL/GA/TX/NC and the like: the new maps are more Republican-favorable than the 2020 cycle's were.
"Mathematically impossible" is a strong phrase, but the House is probably already notionally Republican on the 2022 maps, so the scenario where Democrats keep the House is probably one where there's a swing to them and they perform better than they did in 2020. That's not very likely.
This is an extremely rosy outlook for the GOP. My biggest disagreement with this is that all indications so far are that Republicans are aiming for "least change" maps in their states (e.g. IN/TX/FL), and that won’t amount to "way more" seats than Democrats will pick up in NY/IL. It’s very easy to go nuclear on Republicans in CA (where you obviously don’t have a non-partisan/independent commission) and NY (Hochul has already promised to sign any aggressive gerrymander), and those two states alone would more than compensate for minor D losses in TX/FL (GOP potential here & in OH has always been overblown).
States like NJ/PA/MI (especially the first two) aren’t so much about being
less favorable to Republicans than the current maps but about being
less favorable to them than they should be based on pure geographic distribution of the vote (which is considerably more favorable to the GOP now than it was in 2010, especially in the Upper Midwest).
Realistically, the absolute best-case scenario for the GOP in this redistricting cycle is a wash with more "least change" maps than expected (I’m just not sure that Democrats will play along). I really don’t see much of a net gain for the GOP and never really bought those predictions.
