I don't think Ainge sees Rondo in the future of the team.
I think Ainge does (but he is open to changing direction if the right deal comes along).
Does Rondo seem like a good fit for the type of team Stevens seems to want to build? I think he does.
Does Ainge seem to be trying to build a team with players that complement Rondo? I suggest that his continued search for a stretch 4 is motivated in part by a desire to make up for Rondo's lack of three-point shooting with someone at the other non-wing positions (although a big who can shoot threes at a useful rate is a good thing in and of itself). Ainge didn't seem interested in looking too hard for a young point guard with upside, filling out the roster with Pressey, a guy whose upside is career backup, at best. Ainge seems invested in wings like Green and Bradley who are comfortable playing off the ball next to Rondo.
I believe it fits Ainge's past behavior to have him be willing to build around Rondo, but be willing to trade Rondo if he can find a better player to build around. He might make a sideways trade for a similar-level star. If he trades Rondo for young talent, it will be for someone who he is sure will be a future All-Star, not someone who he hopes has potential to be one.