Well a reboot is really the last place I want the franchise to go. The movies gave me exactly what I want from an X-Men series, I really don't want to see another take on it. It's either going to essentially tell the same thing anyways (Xavier v. Magneto / X-Men v. Brotherhood, picking and choosing which characters to fit the story, and likely not going with an original 5 to start off with, all stuff that was done perfectly fine the first time around. I have no desire to see someone other than Stewart, McKellen, Jackman, Famke, Grammer, etc... in their iconic roles. Outside of maybe Halle Berry, the series was cast perfectly) or it's going to go in some crazy direction that I don't really wanna see anyways (to justify itself, it may go completely opposite this current series and start taking the X-Men into space, battling space aliens, etc... just stuff I don't even like in the comics, let alone want to see in a movie).
And you're right - that can be said about a lot of franchises, and quite frankly, that's when I, as an audience member, begin to tune out is when these franchises needlessly overextend themselves. Pirates of the Caribean was great. I thought it was perfect on it's own. Then they had to go and make 2 and 3, and predictably enough, those movies weren't needed, and didn't re-capture the magic of the first. And now they are even on 4, and I haven't even seen it yet. Terminator and Terminator 2 were an amazing 1-2 punch of movie and sequel. Terminator 3, nor Terminator Salvation were much needed. And alas, they offered nothing to the franchise as a whole. There are countless franchises that I tune out from the get go because a sequel simply wasn't needed, but they are made anyways. X-Men is fast reaching that point. In fact, I think it's already reached it. There was no need for X-Men: First Class. It happened to be an awesome movie, and it surpassed my expectations. But as someone who is a huge X-Men fan, I had the least hype for this movie that I have had for any X-Men movie to come out, because there's just nothing left to do. And I'm sure I will be hyped even less for any future movies to come out.
If they can continue to make quality X-Men movies, then I'm all for it, but I just don't see what's left. And personally, the last thing I want to see is either a reboot, or future films that come out that decide to disregard whatever they want from previous movies and just trek along ignoring events from past movies. In the beginning, X2, X-Men: The Last Stand, and X-Men Origins: Wolverine all had the benefit of adding to the X-Men movie universe, expanding on plot points that were introduced prior, concluding plot points that built up over the course of numerous movies, and overall worked together to tell a larger story. Now? Now these movies just serve to contradict and ret-con each other. Having reached that territory, I think it's time to call it a day on the X-Men franchise and quit while you're ahead.
Unfortunately, the business model is to juice as much money from these properties as you can, which means running it into the ground until it's become a joke. The X-Men movies aren't far from that status.