Yeah, most of the sponsors stick around for the long haul.
As for the #24 being the car to beat, that's based solely on his track record of being the dominant car at Daytona. They've found a set up that works quite well there, and everyone else is still searching for that set up. He was 2nd fastest, if I recall, in practice or warm up or whatever it was.
The few other cars mentioned are sure to be ones to watch as well. The #99 especially, if the team can carry the fire hot momentum they had at the end of last year. Don't rule out the #20 either, or the #8. DEI has all but mastered restrictor plate racing tracks. Remeber to when Dale Sr. wrecked and passed on (may he rest in peace, and not forgotten), it was the #8 and #15 (both DEI cars) were running one two (don't recall the order specifically) with Sr. running third.
I think all of the big names are cars to watch, as anything is possible in racing. One big wreck could take out all the big names, and someone like Kenny Wallace or Ken Schrader could win!