I think there's room for six receivers, plus Slater. It may mean they skimp elsewhere, but it's certainly possible to fit six receivers. I suppose it depends whether you value Nate Washington over James Develin, for instance.
Current locks are:
QB (2): Garoppolo, Brissett
RB (3): Blount, Lewis, Bolden
WR (3): Edelman, Hogan, Amendola
TE (2): Gronkowski, Bennett
OL (5): Solder, Vollmer, Stork, Thuney, Mason
DL (5): Ninkovich, Sheard, Brown, Knighton, Valentine
LB (2): Collins, Hightower
CB (3): Butler, Ryan, Jones
S (4): McCourty, Chung, Richards, Harmon
ST (4): Gostkowski, Allen, Cardona, Slater
That's 33 players who are almost certainly locks, barring injury. There's another few who will almost certainly make the team:
WR (1): Mitchell
DL (3): Long, Branch, Grissom
LB (2): McClellin, Freeny
ST (2): King, Ebner
This gives us a total of 41, and 12 more positions to play around with until Brady comes back.
QB: 2
RB: 3
WR: 4
TE: 2
OL: 5
DL: 8
LB: 4
CB: 3
S: 4
ST: 6
4 of those are likely to be offensive linemen, probably a tackle and three interior linemen, so that's 45. We'll likely get 2 more defensive backs, so we're at 47. Another defensive lineman will knock it up to 48. Now we have 5 slots left. One's likely to be a third tight end, so we're down to 4. Now we can add two WRs and two RBs (including a FB) or one WR and two RBs, or a combination of three skill position players and one player elsewhere (tight end, linebacker, or special teams).
Since two TEs are likely to be on the field for a majority of snaps, I can see rolling without a fullback.
In other words, it's not impossible to imagine keeping 6 WRs. Someone will have to make way for Brady come week 5, but I suspect the final roster will include Edelman, Hogan, Amendola, Mitchell, Washington, and Martin.
