Average 2022 football home attendance by P5 conference accounting for realignment in BIG, PAC, SEC, and Big12.

SEC 78,492
Big Ten 64,434
ACC 48,122
Big 12 47,300
PAC 12 42,632

If you add SMU and SDSU to the PAC, then their average attendance drops to 40,099.

I expect the SEC to rise a bit with UT and OU coming in. Not sure about the BIG. The Big12 will probably be about the same since you have 8 schools losing a game with OU or UT each year but the new schools will probably rise due to being in a P5 conference. The PAC will likely continue to fall, but faster now.