Right now, the deadline that requires SPL or LAPL(S) for EASA sailplanes (including TMGs) is unchanged at Apr 2018.
Thus, nothing published,
however,
I think you can confidently expect a further extension to 2020/21.
Note, this is for flying TMGs on a sailplane licence.
I'm not aware of any extension in prospect for flying them on PPL(A) or LAPL(A).