I've never played a campaign for that long, but from the perspective of a player, I like following up a longer campaign with a one-off session (e.g. a simple dungeon crawl). It's nice, after being so invested in a character, to roll up something I don't have to care too much about because I'm not thinking about using him/her over the course of several levels. I can try out a new race or class, specialize in some exotic weapon, or pick some goofy characteristics for my PC that might be tiresome, for both myself and the group, over several sessions. It might also be a nice break for you, in terms of not having to prep a whole campaign.
So, I guess what I'm suggesting is, start by offering a simple, 1-2 session dungeon crawl, or similar, and see how that goes. It should be pretty obvious if people are interested or not and, if they are, then you can offer something more long-term afterward. Who knows, that intended short crawl might turn into something bigger if the players like their characters.
And, when all else fails, ask the players! Be sure to include the apprehension you mentioned and see what they say. As long as you're open and honest, I don't see how they could think you're a jerk.
UPDATE: My GM just took all the PCs from a short, disconnected crawl like the one I described above and had them show up as NPCs in the following, long-term campaign. Seeing him role play our characters from his perspective was hilarious. Maybe not a reason to do a short crawl, but a cool potential resource for NPCs that your players will get a kick out of.