It's going to be changed to a new forum software which is called Epochtalk (created specially for bitcointalk and will be open source) and not to another Simple machines version. We honestly don't know but I think It's soon as theymos added an announcement on the top last time that we should change our emails to something we control In order to use the new forum later.
I think that announcement was just made in order for us to be able to log onto the new version of forum software at [beta.bitcoinalk.org] altough that site is currently offline - possibly, they're fixing the errors in the github file in order to deploy it to the forum soon.
I assume there will then be updates throughout the new release every few days (hopefully).