Let me preface this by saying I have no specific qualifications. Further, I don't know of anyone that can accurately predict recovery from an injury like the one Walter Thurmond suffered. He tore his ACL, MCL and PCL. And though I have not read any specific reports to confirm or even imply this, traumatic knee injuries like Thurmond's sometimes involve cartilage damage as well. The severity of the injury and his position's reliance on cutting and change of direction are working against Thurmond.
Here's what I think is in his favor.
Time: Deion Branch tore his ACL January 12 of 2007. He attempted a comeback in week five, but then missed the next five weeks in part because of a bruised heel. He returned again in week 11 and finished out the season playing close to full strength. Week 11 was about 11 months from the original injury. Thurmond suffered his injury on September 26. He won't be 11 months removed until the end of August, but should he mimic Branch's timetable, that's about as good as one can expect. He will be mostly healthy for practice and the pre-season and hopefully fully healthy for the regular season.
Hard work and progress: Maybe it's just a fan thing, but I find this sequence of videos heartening.