It's not about this year or next year, it is about the fact that you have to build a competitive roster to be competitive. You have to add talent. If you have to add vet talent, then you either choose to draft and develop players behind them or at other positions. Until you have players who can step into these vacated roles, you hold onto to good, veteran players.
Josh Sweat and Budda Baker are the two best players on this defense and it isn't particularly close. Budda is gone next year due to how his contract is structured. The team isn't in a position to just offload Sweat for 2nd or 3rd rounders.