The annular confinement beam is only used in de/materialization, not transmission. It's the data that travels.
That's interesting if correct but I wasn't able to find anything to support that on Memory Alpha. It suggests that the beam is used to maintain the integrity of the pattern and in some cases the beam had to be strengthened to beam somebody through interference. If the beam is only needed to dematerialise, it would not be needed to punch through the interference.
Scotty was already working on transwarp beaming before Spock's arrival and understood where he was going wrong wrong. He certainly hasn't forgotten how to use it so, given that it requires no modification to the technology to implement
, it can come back at any time.
He has, however, been ordered to stop his research (in the comics).