I'm not sure I'm buying this for a couple reasons.
One is that Houston has tons of young pieces. I'm not sure they want three picks in this draft. Second is that I'm not sure they'd want Teague either because they have two very decent pgs. It would imply to me that they don't think they can resign Goran Dragic or something.
Therefore....putting pieces together here.....I bring you a pure speculative trade.
Celtics get Royce and the rights to Donatas M
Houston gets.....the two picks, Etwaun Moore, possible 2nd rounders, and possible cash
Why it works.....Houston get the guards they need in Moore and Teague and they simultaneously thin out their front court where they badly need to make some more minutes available to guys like Patrick Patterson, Chandler Parsons, Marcus Morris, and Scola. It gives them a good excuse to pick more of a project big man like Fab Melo and/or Festus E, which makes some sense because their big men Scola, Camby, and Dalembert are 32, 38, and 31 respectively. The 2nd rounders allow them to stash things overseas for the future and they could always use some cash.
Why it works for the Celts. Having drafted a Lithuanian before Danny is ahead of the curve on this. Bringing in two relatively mature young players fits the win now mold in Boston. The Celts can't afford any projects. Danny is on record very recently saying any player they pick up has to be ready now. If they lose Ray they will need guys that can shoot from the outside. Danny will want to keep JJJ for his defense. Royce as a ball handler is very helpful in case anything happens to Rondo and also helps replace Paul Pierce's passing skills should he leave us now or later.
Another possibility could be if JJJ lights it up in summer league he could end up in this trade and things could get more interesting.
If Danny has a strong indication KG and/or Ray will leave you could see Kevin Martin here.