Hopefully you can wait and see on the Jets' situation with Thomas Jones before making a call on your keepers, but I would still lean to Shonn Greene. What we are seeing in the playoffs is no mirage -- Greene is for real.
He has had four games with decent carries this year, week 7 @ Oakland (144 yards and 2 TD's), week 16 @ Indy (95 yards), the wild-card game @ Cincy (135 yards and a TD), and Sunday @ SD (128 yards and a TD). Greene may not be a PPR monster, but the Jets should continue to have a conservative passing offense and they have a great young offensive line. Whoever gets the bulk of the carries and red-zone touches should be a beast in any format.
Thomas Jones will be 32 when next season begins, and he is due a $3 million roster bonus in March, and a 2.8 million salary for the season. There's a decent chance Jones will be cut. Even if he doessn't get cut, he could still take a backseat to Greene, the way Ray Rice took over from McClain and McGahee this year.
Not sure how many WR's will get thrown back in your draft, I like Jennings and he had an off-year. But you can always draft good WR's -- (this past year you could've got WR's like Sidney Rice, Miles Austin and Mike Sims-Walker off waivers in a lot of leagues). I'd rather have three great RB's and try to get a decent WR (like Jennings) with the 8th overall pick, or the best QB available, if I was in your position.
Obviously by March the Jets will make their call on Jones and you can make a more informed decision. Hard to pass up Greene with his upside though.
I have the doomsday device!