Molly in S4
I hate to rain on anyone's parade, but let's not get our hopes up unnecessarily to have them later brutally crushed.
Steven Moffat never said Molly will have an "increased role" in season 4. It was written in this article, NOT as a quote, but a weird interpretation of his Tv Guide interview, which the article references. Yes, there is a lot of reassurance about Molly's importance for Sherlock in Moffat's rather evasive reply, but nothing specific about her role in season 4.
Anyway, seeing how Steven is busy with Doctor Who and Mark was with Coriolanus, apart from the ideas they mentioned, they probably haven't written anything yet. So it's still up in the air and can go either way, depending on where the story takes them when they finally sit down to write.