Apple blew it with iBooks 2
Apple failed to change the game with textbooks, and not because of exclusivity agreements or proprietary formats. Apple's mistake was not being aggressive enough with the publishers. You might think of the $15 cap on e-textbooks as being very aggressive, but you just missed the trees for the forest.
The key part of Apple's announcement was that them and their partners are focused entirely on K-12. Why is this? Because that's where the money is for the publishers. Unfortunately, it's not where the money is for Apple. There are so many barriers to bringing iPads to the K-12 classroom. We're talking school boards which are incredibly slow to make any sort of budget changes, and that's assuming they even find this to be a worthwhile investment.
Furthermore, the reality is that it's not a worthwhile investment for your average public school. The only way you could get your average school district to fund iPads, even with the possibility of a reduced price post iPad 3, is if they keep them year over year, and unless schools are willing to let their students take the devices home (unrealistic) then that defeats the entire point of having textbooks and curriculum on the iPad in the first place.
If Apple starts selling college level textbooks at $15 on the iPad then I think they've struck gold, but I don't see that happening any time soon. So what changed? Nothing.