Get the group together and say you're not happy with 4E as a DM and not willing to run it any more. If they want to keep going with your campaign, it's switching back to 3E; otherwise, you will step down and hand the DM screen to somebody else. That's your privilege as DM, no matter what the players think. You are never obligated to run something you don't want to run.
The players will probably want to discuss this and voice their opinions. Let the group bat it around for a bit. Once everyone has had a say, ask if anyone else wants to step up to DM, and if someone does, take a vote on which way to go. If no one wants to step up... well, then, 3E it is, unless the gang wants to knock off D&D entirely and play Settlers of Catan or something.
The players will probably want to discuss this and voice their opinions. Let the group bat it around for a bit. Once everyone has had a say, ask if anyone else wants to step up to DM, and if someone does, take a vote on which way to go. If no one wants to step up... well, then, 3E it is, unless the gang wants to knock off D&D entirely and play Settlers of Catan or something.