Maybe not totally but some big movements in the field of English teaching recently given current research into translanguaging and the marginalisation of other languages.
In fact, the British Council have just updated their statement of approach to reflect exactly this: that an English only policy will no longer be imposed on English teachers in the network.
Long overdue IMO when used judiciously.
A few things immediately spring to mind:
Many schools have discreetly been doing this for years by giving lower level classes to local teachers. Well now there is research out there to tell students why!
However, it will still be a tough sell to parents who expect English only in their kids' lessons (having been told this is the only way for so long).
As more attention is shone on this move, it will only further empower high quality local teachers and perhaps lead to the end of the Khao San Road chancers.
Managed properly - to repeat again, judiciously - I only see this as a good thing.