I interviewed with Williams recently, and was told that the process is indeed rolling, as many of the initial batch they give offers to end up also being accepted to PhD programs and turning down the Williams offers. Also, if you're sure you want to do premodern only then you might want to consider how much you might be able to get out of the program. I was given the impression that their faculty composition right now is heavily leaning towards the modern/contemporary areas.
As for UPenn, I was informally accepted this week for the MA over a call with my poi, after being rejected from the PhD. If you applied for the MA only you should probably expect a decision soon.