What I would really like to see is “subscribeable OPML feeds”, so GitHub could provide a OPML feed for what shows up in your home page, and you any changes in your subscriptions (repos you watch etc) would change the OPML, which would then cause your feed reader to unsubscribe/subscribe to specific RAS feeds.
Unfortunately, this isn’t supported by the majority of RSS clients (tt-rss is the only one I know) which means in practice OPML feeds are merely import/export mechanisms.