First of all, I've never seen you this excited about a goalie prospect ever (except for maybe Knight), so that's a welcome change lol.
Second, I don't think it will cost nearly that much to acquire Portillo. He's a solid prospect, but he's not in that first group of Wallstedt/Askarov/Coss/Levi, and he's not really in that next tier of Kochetkov/Clang/Blomqvist/Dostal/Wolf. In other words, it's not clear if Portillo truly projects to be a high end starting goalie. He may become one, but he may also become a really solid backup or somewhere in between like the second guy in a 1B platoon option. So he would be a great addition for sure, but not sure he represents THE future in net.
Third, it won't cost NEARLY that much to trade for him if he won't sign. In part because he's a pending UFA, and in part because he's not in that tier of propsects. At most, it would cost one 3rd rounder, or if he has an absolute monster year, one 2nd rounder. Just like McBain who was essentially acquired for a pick that's similar to where he was drafted.
Fourth, he's VERY intent on completing his degree. That's his stated reason for not signing this summer. I'm not sure if he can get that done this year or if he needs to go back for his senior year.
Lastly, It's really not clear what his personal desire or objectives are, but even if he's given one game (or a few games) to burn a year off his ELC at the end of this season (which BUF or a lot of teams could offer), he's going to need to spend at least one full year in the AHL next year. So I'm not sure if there's a particular destination/city he wants to be in, but if that's the case he'll just go to UFA and won't sign anywhere and doesn't care about burning a year off his ELC. Given his age (he was passed over in the 2018 draft so he's a year older than his 2019 draft), his ELC will be shorter anyway.