The issue for the Texans is that Stevie Johnson just netted the Bills a 4th. Stevie obviously isn't on Andre's tier, but he's a very good WR, and he's suffered through terrible QB play. Oh, and he's five years younger than Andre. Also, Stevie Johnson's contract is MUCH more attractive. Both players are UFA's in 2017. Stevie Johnson's cap hit 214-216: $3,925,000, $6,025,000, $6,125,000. He turns 28 this year, so he should have 2-4 more years where age shouldn't limit his production. Andre Johnson's cap hit for the same years: $14,644, 583, $16,144,583, $14,675,000. Andre Johnson turned 33 on July 11th.
So, yeah, if you're the Patriots, and you think Andre Johnson still has enough to get you over the top, you should have some interest, but he's really not worth trading for Houston. I'm thinking fifth or sixth round compensation.
http://www.spotrac.com/nfl/san-francisco-49ers/stevie-johnson/
http://www.spotrac.com/nfl/houston-texans/andre-johnson/