The only way to trade for a top 5 or top 10 pick is at the end of the season. If you trade now, you make the other team better, and the pick is out of the lottery. No way someone offers us a top 5 pick for Rondo at the end of the season. Everyone wants a shot at the next Jordan or Lebron.
If we really wanted to tank, which I think is a bad idea, then you trade Rondo and Green for a bunch of expiring contracts for cap space next year and even more draft picks, but the bad teams will all be keeping their picks. Only good teams will want Rondo or Green.