That's it in a nutshell, however, a player offside from a previous play remains offside and thus potentially liable for penalty until he is put onside by his or the actions of other players. I don't see that the ball going into touch changes this.
►Ball goes into touch.
►Referee blows whistle
►How can any players still be be offside now?
Any player that was offside prior to the ball going into touch should have been pinged for offside at that time
►Ball comes out of a scrum, and the Green SH kicks to touch 15m downfield just as Green 8 leaves the scrum.
►Green 8 makes NO attempt to chase the kick and is not within 10m of where the ball landed, so the 10m law does not yet apply to him.
►Red 14 takes a few seconds to recover the ball before taking a quick throw in to Red 15 who is immediately tackled by Green 8.
Who is going to ping Green 8 for offside prior to the quick throw in?
Certainly not me!
Surely, the 10m law only applies if the ball lands in and stays in the field of play, otherwise, there would be no legal way for the for anyone in Green's forward pack to approach the LOT for a line-out.
Edit: On reflection......
The 10m Offside Law was modified a while back. As I remember, it used to be a 10m circle and only became a 10m line across the field relatively recently. However, the 10m Law itself has been "on the books" for a long, long time; certainly much longer than the quick thrown-in has.
Now this issue of whether or not an offside player can still be held to be offside after the ball goes into touch, would never have come up before the quick throw in became Law. There would not have been any reason to specify this, because the ONLY possible way to restart was by a line-out, which REQUIRED players to approach the LOT, and has its own offside specifications anyway.
Speculation: I do not believe that the Lawmakers ever intended for the offside law to apply once the ball was in touch. I believe that it has only become an issue since the quick throw-in was introduced, and has been further thrown into stark relief by the ELV's introduction of the angled quick throw.
IMO, the ball is dead while it is in touch.
DEFINITIONS
Dead: The ball is out of play. This happens when the ball has gone outside the playing area and remained there, or when the referee has blown the whistle to indicate a stoppage in play, or when a conversion kick has been taken.
A ball in touch is outside the playing area.
► You cannot tackle a player holding the ball when he's in touch
► a player cannot advance the ball to any position further upfield than the LOT
► a player can pass the ball forward (no wisecracks about "momentum" please!) to any other player in touch.
Only once the ball comes legally back into the field of play does it become alive again. The only thing that the law allows to be ruled when the ball is outside the playing area is foul play - Law 10.4(l).