Current RSS readers are more or less similar, differentiated on interface features rather than core functionality, and sold, where applicable as software tools.
Over time these features will surely be a commodity and any business model around RSS aggregation will be based upon the value add on top of aggregation.
My guess is that this value-add is in efficient searching, categorizing and personalizing rather than discovery and display.
Categorization and personalization can be done by adding metadata to existing feeds (the tokenization process of search could arguably be considered metadata a tokenized content tag would allow local searching). This can be entirely independent of the tool used to view RSS, providing that RSS readers can read this metadata.
The time is probably about right to start looking at this from the various initiatives such as FOAF and RSS topics that are out there and building features based upon them into aggregators.