I do like a cynical man. We are so rarely disappointed by expecting the worst of peopleYes the tanks will stay as they are. Tanks neck thread is mostly M25.
Unscrew your single tank valve/twinset manifold. Insert new valve/manifold. Change DIN part of reg to new M26 or replace reg completely. Viola!!
You now have the same tank, same reg and a bill for 60 quid+. Fill with trox as before.
Improvement to safety of scuba diving - nothing. Improvement of sales figures of suppliers - considerable. Likelihood therefore of overturning legislation - go figure.