I voted the 80 to 90 range... it's the safest bet.
I highly doubt that this is going to crack the 90's but i've been wrong before so...
It will have stuff going for and against it like any movie. The pros will probably be the many surprises saved for the theatre, the emotional "goodbye" to several characters should enlist a strong reaction, also this really being the culmination and resolution of everything that went down in IW...
The cons could be the length of the movie, the fact that a lot of it will be undone and serve basically like a reboot of the universe and with that comes the argument to the potential lack of stakes, the extensive use of CGI... A lot of these are basic complains and some could even be argued either way.