The negotiations, I believe for the final two seasons (leaving us where, say, with Nixon getting elected in 1968? New Year's Eve 1969/1970?), took a long time, so we probably won't see new episodes until into the Fall at the the earliest. It'd be interesting to see Don Draper competing head-to-head with all the fall big network shows, as it's always been the summer up until now.
But he's back. The only bummer is that it'll be more than 39 weeks since we last saw a new episode -- closer to 52.