For many of you, after reading these boards I see that you aren't exactly familiar with more sci-fiesque genre of shows. The 4400 of course is one show that seems to bridge the gap between sci-fi and a great drama show. I love it!
Now, general practice for sci-fi type shows (as you may remember for those of you who watch The Dead Zone) they split the seasons in half generally. They take like a late summer break and generally return January or February. Of course, the reason why is because it allows them to re-run and gain additional ad revenue. But it also allows the actors a time to have off more with their various activities and family time during the off season.
Anyways, take heart, I highly doubt it will be next summer and this will only be a 13 episode complete season. For a show like this, with the nominations it recieved, the viewership is too great to pass up a full 20-24 episode season in commercials.