Over the next few days, wmf13 will be deployed to WMF wikis. We mostly worked on small fixes this week and on the cawiki deployment, so there aren't that many exciting things in wmf13. Some of the more noteworthy things new in wmf13 are:
Sorry, that was copy-pasted from the wmf12 email. We did in fact do exciting things in wmf13, the TOC change was pretty big for example.