In all the Kevin Love threads, posters generally assume Kevin Love would be willing to stay in Boston, or anywhere else he is traded, and that a trade would not happen without such a declaration. He can promise all the team trading for him wants, but that's the extent of it. Unlike when we got KG, there is really no way for him to sign an extension that he'd be willing to sign. If the Celtics traded for Love, they could ask him if he'd be willing to re-up in Boston, and he could say yes. However, he can't be held to it. If he didn't get along with Rondo, or the team still lost, or he just doesn't like Boston, he could pack his bags and leave next summer, a la Dwight Howard.
The same is true for any other place he's traded to. The Celtics, and any other team pursuing him, really need to be confident that you can keep him. Otherwise, you have nothing after a year. This is why I think the Celtics should be very wary about trading for him. I'd love Kevin Love on the Celtics -- I've liked his game since college (especially his outlet passing, which is a thing of beauty). But as a one-year rental? No thanks.