While its very unlikely Welker is traded for all the reasons stated before. Its NOT a dumb question. The Pats have a wealth of experienced depth at WR.. The offense would still have as many or more "go to" receivers as any team in the league, without Welker.
They could roll over the the wealth of cap space they would have into next season, because they will have a larger than usual number of contracts that will need to get done. HOWEVER, all that being said, I think one of the real sticking points in trading Welker is what would you get for him?
Given his age, size, and accumulated wear and tear, I really don't think there is a big enough market that would bring the kind of package that makes Welker worth trading. Remember the team that trades for him has to not only give up significant draft picks, they would have to sign him to a LT contract (essentially over pay him), as well. That will surely depress the market.
The only team that would give a high pick AND pay for the contract would be a badly managed team that field they are a WR away from a superbowl, much like Seattle did with Deion. (and that trade was a disaster for them) So whatever pick you got for Welker, its likely to end up in the bottom third of the round. Based one what other people have given for good WRs, at best the Pats would get is a 2nd, and more likely a 3rd in trade.
BOTTOM line - Wes Welker is easily worth more to the Pats this season, than a bottom of the 2nd round pick. Especially when you consider that if he walks next year the Pats are almost assured of a 3rd round comp pick a year later
The issue has and always will be a philosophic one. Do you pay for past performance, or do you pay based on future expectations? If you believe in the former, you give Welker the 9-10MM/yr he wants. If you believe in the latter (which I think is where the Pats are at), you hold strong to that 6-8MM/yr you are offering.
Other thoughts on this issue
1. I can't hold a pity party for a guy who will have made close to $30MM in 6 years as a Patriot. The Pats FO are not the bad guys here (and neither is Wes)
2. Wes has more value to the Pats than any other team, if only for the connection he has with Brady. Conversely Welker is more likely to be successful here than anywhere else.
3. One off the wall comment. Welker, over the years, has become Brady's safety net, much like Ben Coats was Bledsoe's go to guy. There ARE times when I think Brady looks to Welker too much. That he goes to him when other guys are open. I can't help but wonder if Welker weren't there, if Brady would go back to spreading the ball around more. Much like we saw after Moss was written out of the offense. Just a thought