Each item that appears in River2 has a like RT link at the end. Right now that link is configured to the tool I use for my linkblog, Radio2. Given Dave's noteblog development, it seems logical to me that River2 or River3 will be connected to Fargo rather than Radio2.
I can see Radio being put to pasture. Fargo is the logical next iteration of Radio2. Dave has said that he is working on a bookmarklet to send links to web pages to Fargo. My understanding is that it is the same as the Radio2 bookmarketlet that exists today.
In a way the bookmarklet eliminates the need for that RT link, but personally, I like the idea of a simple link at the end of an RSS item that I can click to blog about that item.
What this means is that slowly, Fargo is becoming my lone blogging tool. In fact, from a blogging perspective, it might make sense to combine River and Fargo together. River just becomes a menu option for Fargo, I select it to read my news feeds, I click the "RT" link to send an RSS item to an outline where I can write additional commentary about that link.
Note that there is a definition of blogging that is emerging from what I write above, and it relates to what I wrote earlier that linking != sharing. Blogging starts with reading content on the web, deciding that you have a point view about what you read that you want to share, then grabbing the link to that content and writing your point of view, and finally publishing the link to the content and the point of view to the web.