I don't think that's right. BB-Marin a few posts above implied that the conference winner promotion thing is around for this season, and then will be gone for season 30.
64 spots in D2. 16 of those promote to D1, 8 demote from relegation matches, 16 more auto-relegate. There are no bot demotions that won't be relegated the normal way. So that means D2 has to have 40 new teams next season.
So there's enough room for the 32 D.3 conference winners as well as 8 teams who have the best record across D.3.