I think we may get a few surprises on the new site, so maybe there will be some new games, but besides that I believe all the games will be migrated to the new one and then games will be posted regularly. as Ghgt99 said.
Every game that AG has now is also on Beta. So from this, all the games were migrated to Beta. The newer games, as well as games fresh out of the oven, also go to the new site. With this, we can assume that Beta will function just the same as AG2: All the games we have come to know and love will be on the site, and we can expect the rate of flash games to be the same. There isn't going to be a feature that will speed up or slow down the rate of flash game submissions or anything--that would be weird!
Sure, there will be a few huge surprises. Exit path 2, raze 2, and two huge mystery games hero interactive will announce on his blog. Not that this have anything to do with ag3, though.
I think I heard once that it constantly updates every 15 minutes or something. So if you see a new game on AG2, wait 1 hour and it will show up on AG3 I think.