There's also a flat cap which most contending teams are up against. 17 teams have less than $1M in cap space right now. Only six teams, including the Preds have $10M+ available (assuming he's looking for that much) and ours includes the current $6M for Forsberg.
The others with enough projected space to sign him in the $9-10M range are Ottawa, Detroit, Anaheim, Columbus and Arizona. Of course teams can move out some salary for next season to fit him in, but it's not always easy.
I think re-signing here gives him his best chance to get a huge payday and play on a competitive roster that is on the upswing.