Seattle has to decide whether to exercise the 5th year option on Penny this off-season. Not sure what the commitment would be, but he hasn't shown that ability yet. Plus Seattle is without a 1st and 3rd in this draft and need help at DL, CB, and OL. Any RB they add would be a late pick or a UDFA.
Homer is more a 3rd down back. Dallas was a former receiver, so he's a good pass catcher, but not an every down back that Seattle is looking for to bring the physicality.
Carson, depends on what he wants money wise. 4 years at $40-$45 mill is probably the max Seattle goes with $20-$24 mill of that being guaranteed.
Thing is, what other team would pay for a RB? He's not a hybrid back, a clearly a much better running than receiver. SEA and Carson fit each other well. See if they can make the money work. Seattle has to pay to keep dunlap and Adams is done his 4th year and wants to get paid. KJ Wright a likely cap casualty, but with the selection of Brooks, they should be ok at LB. Also Griffen at CB is a free agent.
Yup, it will be decided by the offers he sees when he hits FA and from the tone of Carroll's answer they won't be offering first.
KJ is another matter because his play has been fantastic all year. Ol' reliable, and smart. I think the team will want to keep him around if at all possible. He's going to have to accept less than his current cap hit but given his age and desire to finish his career in SEA I could see it happening. Naturally Adams and Dunlap are the higher priorities.