Any team not named Clippers would love to have Rondo, but nobody is going to overpay for him in order to make it worth for the Celtics.
Rondo is a star, a special player, top 10 in jersey sales, you need that kind of players to stay relevant in spite of your lousy record.
Rondo is the best passer, and more prolific assister in the NBA.
Rondo is still young, not only in age, but in NBA years. Rondo and Green are the same age, 27, and they're still maturing, so you could say that Rondo, entering his 8th season, and Green entering his 6th season can give you a good core for you immediate future.
It would take a big offer, regardless of the #1 #2 options narrative, to separate Rondo and the Cs. This is Rondo's team, and unless you are offering an All Star and a potential franchise player, you're not getting it done, IMO.