ESPN's SportsCenter Twitter account (via ESPN's Chris Mortensen and Jeff Legwold) reports Wes Welker is unlikely to play again until the postseason:

Mortensen and Legwold provided additional context via ESPN.com:
The team's hope is that Welker, who left games in Week 11 and Week 14 with concussions, will recover in time to play in the postseason. Welker continues to be evaluated by the team's medical staff and an independent doctor as part of the league's concussion protocol.
A third concussion in such a short span could end Welker's season, and one source said the player's well-being is "still the highest priority."
Welker has not been medically cleared to practice, but on Thursday he spent some time working with the strength and conditioning staff in the team's weight room.
Gray Caldwell of DenverBroncos.com reports that Welker is officially out.