Pure speculation and opinion, but
I think Corey Maggette will set the market for James Posey. From what I've been reading, the tiers for at the 3 go
1. Josh Smith
2. Iggy, Deng
3. Maggette, Posey
4. Childress (he'd be higher but for inexperience, and he may get more money anyway due to age), Pietrus
5. Azuibuike, R Davis
6. Everybody else (Devean George, Bonzi Wells, etc.)
Since Smith, Deng and Iggy are all restricted FA's commanding sizable contracts regardless, the FA scrum really starts at tier 3. Maggette has an outside shot at getting more than the MLE, Posey is almost guaranteed to have an offer at the full MLE, but years seem to be the holdup with him. That considered, its pretty likely that they will sign for pretty comparable sums of money.
I think the reason we haven't signed posey is because we're waiting on Maggette to make a decision before we give Posey our true offer. I also think thats a pretty common theme around the league. Posey's agent on the other hand probably realizes that years will go up for his client as the need for him becomes more urgent. With Maggette off the market, teams needing a starting 3 or very capable "gem" in their second unit will have less leverage, possibly inclining them to increase the years. Mark Bartelstein has been pretty respectful in saying "The celtics haven't given us what we want...yet" There is no talk about bad feelings, or loyalties, because he knows he'll get a better deal than the sub 5 million per we're offering right now as our options dwindle.
As I said its all speculation, but what do you think?