I think it's less likely for late summer, more likely for autumn, given that they can't even yet tell us when in August the merger is technically happening. I would think they have to get that out of the way before they can worry about announcing a new promotion.

I wouldn't surprised if isn't some simply-scalable promotion (X number of points for each stay or Y number of points for each night after the N'th), simply because they may not know until the last minute what the start and end dates might be (and more complicated promotions like stay NN nights to get ZZZZZ points don't work very well if they're not designed to a specific promotion duration). Plus they've tended toward those simpler promotions of late anyway.