If it does happen I'd be surprised if anything major changed in the foreseeable future.
Nor do I see an Optimus meets Mickey crossover being any more likely than it already is.
I would presume both Paramount and IDW wont be giving up their licenses any time soon, It's not like Marvel got Spiderman back when Disney took over. it was pretty much business as usual. Correct me if i'm wrong but i'm pretty sure Boom studios still has the license for Disney characters in comic format, it's not like Marvel has added Darkwing Duck to the Marvel Universe or anything.
And for Hasbro I think it will be much the same. Hasbro already make a lot of toys from Disney licenses and some that Disney now also owns. And despite there already close relationship Disney also have a whole lot of other companies producing products for them, sometimes really badly, anyone remember the crappy toys for Tron legacy and Pirates of the Caribbean?
I'm pretty sure Disney understands branding that's one of the reason their building this mega empire, and I'm pretty sure they understand that sometimes it's better not to have a big Disney logo on things.
Anyway them purchasing Hasbro makes sense, they need someone to produce the endless merchandise spawned form the next six Star Wars, Pirates, Marvel films.