Well first of all, in most of these situations, nobody really knows what's going on. I'm sure both Ainge and Posey's agent are trying to distort reality through the media. For all we know, no team wants to offer Posey more than two years; but we all know that Posey's agent is going to say that and is probably leaking info to the contrary.
That said, Danny's playing a dangerous game if he doesn't bring Posey back. I worry that he--like some people on this board--has the mindset that he's the new Patriots/Red Sox, when nothing could be further from the truth. Both in terms of construction and the simple nature of each sport, the Sox and Pats' "tough line" approach has little application to the C's current situation.
1) Age. Brady is Pierce's age in a sport where he could play longer. Brady was in his 20s when they won their three titles. Thus, Bellichick could always afford to take a temporary hit because he knew his window to win a title was wide open. It's similar with the Sox. Though Ortiz and Manny are older now, they weathered the storm in '05 and '06 and came back and won in '07. That's not happening for the Celtics. They can't afford to be tough about salary because they don't have a year or two to wait around to find a suitable replacement.
2) Speaking of suitable replacements, that's also something the C's don't really have the luxury of having. People forget, yes, the Pats cut Lawyer Milloy, but they brought in Rodney Harrison. Yes, the Sox let Pedro go in '05 and Damon go in '06, but countered with the acquisition of guys like Beckett and Lowell. Who are the Celtics going to replace Posey with? Giddens? Maybe if we're very lucky, but he's not going to get away with what Posey got away with as rookie? A guy like Barnes? Maybe, but he doesn't have all the intangibles Posey has.
3) If the C's lose Posey and somehow win it all next year, good for Danny. In Danny I will trust; however, if they come up just short, it's an enormous waste. In life, I'm someone always looking to the future. But what's the point of looking to the future if you're the Celtics? The whole point of being a professional sports team is to win a championship. The C's are doing that right now. While I'd like to see them continue that success 5 years down the road, reality will tell us that even if Danny plays his cards right, they probably won't be winning a title then. Remember, every era of basketball has a ton of good teams, but few of them ever win a title. So to risk not winning a title when we're currently one of the "great" teams of an era is crazy. Because even if Danny develops youngsters and clears cap space, it's far more likely that the next incantation of the C's is the '97 Jazz (or worse the '01 Sixers or '02 Nets) than the '97 Bulls.
