I'm excited about the new Spider-Man movie too. Maybe even more so than Avengers, although it's hard to compete with all the hype that has building up from each of the individual origin movies.
As I understand it, Marvel can use the prior characters notwithstanding the earlier movies. After all, First class featured Prof X, Magneto, Mystique, Beast, etc. I think it was a conscious creative choice to mix it up so they didn't look to be rehashing the same ground, much like the Spidey reboot has the Lizard and Gwen Stacey instead of Green Goblin and MJ.
Sentinels would be awesome.
I started reading X-Men sometime in the early 80s. I still have original comics for something like issues 100-300 solid, and about a third of the 1-100 issues, plus all related annuals, special issues, mini-series. I used to buy every cross-over appearance and every X-title, but then it just got out of control sometime in the 1990s so I stopped. Hopefully they're still in decent condition in those mylar bags in long box storage.
IIRC, Banshee debuted in the issues leading up to #100, when they introduced a stereotypic ethnic character from various European countries who always went around saying things like "Mein Gott!" (Nightcrawler) or "Lenin's ghost!" (Colossus) so you didn't forget which country they came from. The original X-Men had been captured by the mutant island (K-something) so Prof X recruited a new group to go save them, leading to too many X-Men and the departure of most of the original X-Men (who went on to join the Defenders). Except Thunderbird, the token Native American who died almost immediately like Ensign Ricky.
I don't remember when Havok debuted. I never liked the Starjammers.