I, personally, don't think they'd do another season if they thought the gimmick wasn't going to last much longer. Judging from the commentary on the Season 2 DVDs, it really seems like they want to put out a high quality product and they'd pull the plug before going to the well one too many times.
That being said, I'm HYPED~! about the season being two weeks away, and I'm still a bit skeptical about whether or not Palmer is really alive. After all, they pulled a trick last year with showing the alternate ending to the extras as a diversion for the internet crowd.