My sentiments exactly. It's not like there were any open-ended questions hanging out there for Banshee and Havok. It's not like we have this "cliff-hanger" involving them and we must have them all back in the sequel to tie any loose ends up.
The truth is, neither Havok nor Banshee (or any of the others being dropped) are among the most popular, upper echelon of X-Men characters. They just...aren't. And believe me when I say...the main movie going audiences are NOT going to miss them. They are going to be focused 100% on the main core again: Wolverine, Xavier, Magneto, Storm, Rogue, Bobby, etc.
"miss them"? Probably not. But anyone with half a brain will note their absence and question it. And if there is a brand new group of supporting characters in the FC time period, most sensable movie goers will just wonder why they just didn't stick with the characters that were just introduced.