Fun fact: Brad Fitzpatrick, author of the original (in C) memcached is now part of the core Go team at Google.

One thing he did was write this memcached client lib that is used for Go on AppEngine: https://github.com/bradfitz/gomemcache

But I'm not sure a new memcached server in Go is coming, I think he is more interested in his 'copious' spare time to hack on Camlistore: http://camlistore.org which is a really cool but a bit hard to describe project with lots of Go code.