Yeah, I'm not sure why there's a sentiment of "oh the Pats will NEVER carry that many WRs"... why not? They've been using their WRs a lot more and the TEs don't see a ton of action. They made the move for Sanu to shore things up, that's not something you really do when the position is already fully stocked.
Edelman is the #1 but needs to be kept fresh, Gordon needs time to heal but is a valuable asset and I can't envision them cutting him, Dorsett is a major contributor this season already, Meyers is an up-and-coming player that they clearly seem to value, Sanu was just traded for, Harry was activated so they obviously intend to bring him back (and he's a first-round pick), Gunner is the primary PR who's performing very well in that role (and didn't look too bad as a WR in limited action, to be honest), and Slater is Slater.
They've really got 6 WRs who are actually full-time WRs, one WR who is really the PR and a developmental WR, and one ST-only player listed as a WR. When they're featuring WRs as much as they are, 6 WRs isn't really all that crazy. It's almost a necessity.