I think that the G20 will discuss more important topics than the cryptocurrency. Now there are more dangerous problems
Obviously there are more important issues than cryptocurrency, but every one of them boils down to money i.e. regular currency, and currently cryptocurrency is the biggest threat for regular bank-regulated currency. So at least some attention will go to cryptocurrency, as well.
Currently almost all of those countries have some stance on that topic and maybe after they discuss it, a more coordinated approach will evolve. If it is good for crypto - we shall have to wait and see.