Good summary of why the Celtics may be a more attractive free agent destination than what popular opinion estimates. But the thing I disagree with is that everything has been building up to this particular offseason. That's just not the way Ainge does things.
Everything Ainge does is for flexibility and maintaining options. He's stated this countless times in his interviews, and his decision making supports it. Prior to 2007 he built up assets with the idea that, at some point, a superstar player might become available in a trade. That scenario finally did, and at that point Ainge pounced.
Last offseason the Celtics had plenty of cap space, but no big-time FAs that the team courted gave them a meeting. So what does Ainge do? He runs it back via FA deals for Johnson and Jerebko that include non-guaranteed second years, in order for Ainge to maintain the flexibility to sign a FA, trade, or whatever a year later. In the meantime, the team competes hard, raising the profile and value of its young players, its head coach, and the franchise in general.
Of course option #1 this offseason is Durant + whichever other max or near-max player. But Ainge understands that you don't gamble on low-probability scenarios. If "that guy" isn't available this year, you continue to build your team through the draft and tactically with trades, all the while keeping your options open.
It's a brilliant strategy. Ainge isn't so shortsighted to focus on one particular year, one particular player, or one particular path to winning. He's playing chess. Just a great GM, perhaps second only to the god-like Sam Hinkie.