I don't think it's hard to see the above. The question I would have is then why wouldn't IU expect to see similar improvements? Green went from 34% to 41% on more attempts, Durham went from 29% to 35% on more attempts. Phinese is at 31% this year and I would expect him to make a jump this coming season. Franklin shot it at 40+% his senior year. So that's our four main guards. If 3pt shooting was one of if not the biggest weakness we had, and following the same logic you laid out above, it would seem like this won't be much of an issue this coming season.
Again, this all comes back to not seeing much of a difference between Purdue and IU this coming season and certainly not seeing Purdue at 3rd and IU at 9th. The gap isn't going to be that big (assuming no injuries to either team and no more players leaving/adding; if there is we can reassess).