We are going to do RSS feeds of topic grids, and also email updates. I don't know about topic RSS feeds.
But you'd probably get what you wanted out of the topic grid rss feeds we are going to make (e.g. if you have a feed fo the My Posts grid, you'd see updates whenever any of the topics you've replied to has a new post).
In either case, we aren't considering a lot of features right now, our next priorities are the email updates and the questions (the tools to mark them answered to get them off the unanswered list). After that there's still PMs and search. We'll get to some small feature additions before then but want to avoid feature creep or those priorities will shift too much.