Don't get me wrong, FTW, I really like Gaffney. I just think his injury kind of clouded the picture, especially if MoLewisRocks is correct that it is a quad injury that may take several weeks before he can fully extend himself again.
As far as the receiving depth goes, a WR4 will be added very soon, or at least I would imagine after the first game in a worst case scenario. I'm actually guessing that it may be one of Branch or Gaffney.
In the meantime, we still have the top 3 receiving options from last year in Welker, Gronk, and Hernandez. They have also added Llyod to the mix to improve that area. Edelman has appeared to have a better camp and is supposedly improved his route running/development skills.
There's also the fact that the screen game will be back too. All of the statistics point to last season being a very 'down' year in the RB passes, so I would expect that to go back to normal. IIRC off the top of my head, last season we only had approx. 30 or so RB passes caught, whereas most years the number has been anywhere from 55-75 or so.
There are still plenty of receiving options right now. I think many are making the mistake of simply looking at the WR depth as of the current moment, and even that will change very soon, most likely after the week one salaries are not guaranteed any longer.
At any rate, the depth will be addressed, even though the WR3 position has only produced minimal numbers in the past 5 seasons anyway. In my opinion it's a major overreaction and Belichick simply took advantage of having some receiving beasts in our TE's to save a roster spot or two, but he'll most likely address the depth that everyone is so concerned about.