No, he has addressed this many times that it will be a one-time thing and he will definitely return to his usual updates of about 2000 renders. I think he's just testing the best way to promote and sell the game on Steam.
As for progress, usually people mean "seggs when" by progress, well, it was promised that S2 will be adult and there will be lewd scenes. How lewd they will be is hard to say, at least we saw full naked Cheeto and Mila in the previews
Honestly, I've never been that curious about the main story in SG, for me it's more about the dynamics of the relationships between the characters, relationship building, emotions, drama, that kind of thing. Judging from the renders, there's going to be a lot of content about them living in Nick's house, Nika, Nami, Mila and Robin moving into that student house, and we'll see more of Katie, for me that's enough progress to make me want the next update.