This will not happen. The two things serve a totally different purpose. I zoom through my many RSS feeds every day in Google Reader to catch up on the news (with context!) It will take me day's to do this in Twitter. Plus, Twitter is horrible as a informational source. Breaking news, yes. Catching up on the latest topics, noooo.
I'll give this 10% of a thought the day you can subscribe to a twitter feed and not have it delivered via RSS...
Is twitter a new feed reader? Sure for some people, but is it replacing RSS as a delivery format? heck no.
No. Twitter is a single website. RSS is a format used by hundreds of thousands (if not millions) of websites.