I know most of the developers working on replacing Google Reader are doing just that -- creating products and services that do more or less exactly what Google Reader does.
But there is another kind of aggregator, river of news, and its needs are pretty simple, compared to the Google Reader approach which requires synchronization among different clients. If I had the time here's the software I would write.
A feed scanner that accepts OPML subscription lists and generates river.js files.
This is the core of a River of News aggregator. It doesn't say how to display it, but there's an excellent jQuery app that does this, written by a group of developers led by Nicolas Gallagher. And it also leaves subscription management to other tools.
It would be great if this core feed engine could easily be deployed in an EC2 instance and very lean so it could scan lots of feeds for lots of users.
It would be really nice to have this simple problem solved once and for all. And it's relatively simple compared to the problems of synching.
For some reason this isn't being discussed. It should be. River of News may not be the only way to read RSS-based news, but it's a good way. And for some people such as myself, it's the only one we need.