I don't think it's cynical. Given the number of reboots the Legion has had, it's a smart thing to do.
But I think it serves multiple purposes. Yes, this new Legion can now be easily discarded if it fails, but it also keeps the old continuity alive in the minds of the older Legion fans like me.
It also gives everyone a clean starting point so that we all learn about this new Legion together (through the eyes of Jon Kent as I've been saying for months). This way, Bendis is not replacing the old Legion; he's simply adding a new Legion 100 years later.
I find it to be the most elegant way of doing yet another relaunch. You can't put a new Legion comic out there and expect fans to learn 60 years of Legion history plus all the retcons in order to enjoy a new comic. They just won't do it. Quite frankly, I myself wouldn't do it.
This way, we get the essence of what was cool about the original Legion -- a bunch of superpowered teens in the future forming a club. That's all anyone now needs to know about the team. Bendis can then build up from there. I'm hoping he won't bother to address what happened in the 31st century and how things have changed in the 32nd because that would then be bringing back all the stuff from the past that makes the Legion a very daunting comic to get into for lots of people.