Not a chance in hell.
Billups is on the downside of his career while McGrady is still in his prime. From an organizational standpoint, that makes it unappealing.
Billups and Prince are better defenders, but McGrady can score in more ways than Billups. From Rick Adelman's standpoint, why would an offensive-minded coach trade offense for defense???
I know, it sounds good in all the tabloids, but where does it get the Rockets? Outside of Billups, nobody on that team will be able to put the ball on the floor and get to the rim, and you don't want your PG doing that every trip down the court. Besides, Billups is the type of point that flourishes in half-court sets, not in the full court. He's a guy who likes to penetrate and kick and break a defense down. On the flip side, pass-first PG's like Kidd and Nash love the full-court game because it opens up passing lanes.
I'm not going to get into all the reasons that it's wrong, but it basically takes the organization back a step. Everyone is looking at the trade as talent-for-talent when it's actually trying to find the right guy for a system. Billups and Prince aren't those guys, and who would be the Rockets' primary scorer from the wing, anyways?