There's no reason to move on from Penny if he can be had at a reasonable price. Dude has given his body for the team. Yes, his body has not held up well to the NFL, but there's always the chance that Penny "learns" how to avoid injury just a little better, and that he's been "snakebit" between the ACL a couple years ago and the lower leg freak injury this year.
Last report I knew was that Penny is on track for a full recovery. When healthy, Penny IS a top-5 NFL running back. Seahawks wouldn't be in the playoffs without him this year, and his difference-making contributions in a couple of the early wins.
Penny for 5 games and +2 in the WIN column was worth it this year. He'll be worth it again next year and the year after, if he can be signed at a reasonable price with an incentive-laden deal.
Carroll's system takes a toll on RBs. We need to draft a couple fast, move-the-pile running backs wherever the value is. 2nd round, 3rd round, or maybe even 1st round for the right talent. We could have had Jonathan Taylor in the 2nd a few years ago but took Jordyn Brooks. The Cowboys picked up stud running back Tony Pollard with a 4th rounder.
Walker was a great pick in the 2nd last year, and still posters here pooh-poohed the pick's "value" even though that pick turned out to be at least a +3 in the difference-making column for WINs. Walker torched playoff-bound LA Chargers on the road with his long TD run with the famous pic of the female fan giving him the double bird.
Carroll's system is severely handicapped without at least one healthy bell-cow running back available every game. Penny and Walker have both shown they can be that guy, when healthy. Let's go after another in this draft.