Here's a mediocre trailer for the new season on YouTube. According to the Wikipedia article on Lost, it looks like there are at least eight finished episodes "in the can" for Season 4 out of sixteen episodes anticipated. The writers' strike may have an impact on when the second half of the series airs.
Also of note in the Wikipedia article, the following regarding future seasons/episodes:
"In May 2007 it was announced that Lost will continue for its fourth, fifth, and sixth seasons, concluding with the 117th produced episode in May 2010. These three final seasons will consist of 16 episodes each, running weekly in the spring uninterrupted by repeats."
I can't remember being as excited about a television series as I have been with Lost. If you haven't succumbed to its siren song, there's still time to catch up on DVD before Februrary!
Lost is like X-Files - it will eventually get so overblown with its mysteries that only its die-hard audience will care.
2010 is a ways away - plenty of time to avoid actually getting to the bottom of anything.
and they've reached an agreement with ABC to run for 6 seasons, no more, no less, so all the questions will be answered and they'll have to start doing more answering than asking soon.