I really doubt he's going to be involved in a S&T -- Just no motivation for him to do that.
There's no reason for him to be able to use his Bird rights for him to make more money on a team over the cap that is likely a contender?
The Bird-rights issue is tricky, because if we're trying to maximize cap space, we're going to renounce everyone's Bird rights (otherwise, there are huge cap holds that basically mean we don't have any space). But, since we're unlikely to spend cap space on new free agents (the FA crop is mediocre once you get past Deron Williams), we might *not* renounce everyone's Bird rights... unless there's an opportunity to make a trade for someone, and now we need cap space.
It also comes down to what kinds of contract offers Ray is getting. A few months ago, he looked like a guy likely to command something a fair amount above the MLE. More recently... not so much. Some of that may be health-related (is Ray starting to show his age?) Some of that may be skill-related (it does seem harder and harder for him to get free).
If he's not getting an offer that's better that the MLE, there won't be any need for a S&T.
Also, gotta figure that the teams that could most use Ray Allen's services are Miami and Chicago. If the C's still hold aspirations of competing next year, they're probably not going to be incline to facilitate Ray's signing. And, I believe the C's will re-sign KG and keep both Pierce and Rondo, meaning that I think they're trying to reload on the fly.