The idea behind RSS is that you like something someone is doing enough to say "hey, tell me every time this guy (o site) publishes something new".
The idea behind social sharing sites (such as Twitter interest graph presented through Flipboard) is that you connect to people you share interests with and if one of these people find something interesting enough to share it you say "hey, tell me what this guy is sharing because I want to know too"
Lately human curated social sharing has been trumping automated RSS news discovery. Why? The difference is in the extra step of curation and validation that someone is doing when they decide that something is good enough to share vs always automatically sharing something with me just because its new from someone I have previously said I find interesting.
The irony of this last part is that the exact same "problem" with the automatic sharing because of past indication of interest is still happening, only it is happening due to a different entity. Previously the entity of interest was the publisher, now the entity of interest is the sharer. Just because I said i'm interested in this guy in the past I will automatically get told "every time this guy publishes (shares) something new". Same concept different context.
I wonder if the next thing to trump social sharing will be where the relationship between your interest and the thing you are interested in is the actual content itself.... but that just seems like way to much work.
Now theoretically RSS could cease to exist and I could still have the exact same benefits that I had during the heyday of RSS feeds and readers. One simply has to "follow" each of the site publishers of an RSS feed and then hope that these publishers posts each new post on Twitter (a task that is probably automated already).
One thing is clear: Reading all new items fell from grace when the unread count of an RSS reader became to hard to keep at zero, much like the Inbox Zero problem... the problem statement remains the same: my time is precious, help me spend it wisely.