I think the prospect of trading Jones is coming up due to a handful of factors. I don't really care one way or the other and trust that Belichick will do the right thing, but this is what I'm assuming posters are thinking:
1) We could save 8 million dollars. That's big. If not, he'll likely be gone next year anyway.
2) He was already likely going to be the odd man out of Collins, Hightower, Jones anyway--which may be why Belichick added 3 DEs in the offseason. Now we can throw Malcolm Butler in the mix as well, which makes the situation even cloudier.
3) Some recent signs of immaturity with the substance situation, and it's possible they may be leery about a potential suspension and/or giving him a longer term pact. We also don't know what stage of the abuse program he's in and if he's had any other problems.
4) He may have been difficult to sign regardless of any other upcoming FA, as Belichick isn't quick to hand out big money pacts, especially ones that will demand the kind of market value that Jones would on the open market.
5) He just hasn't played consistently enough and keeps falling off the 2nd half of the season.
6) We obviously are going to be more limited in draft resources, so that adds to the possibility/"need" of adding to our selections, particularly with a higher round pick.
7) The emergence of Sheard, who we can also save on his 7m dollar cap hit by extending this offseason.