Database sharding and other high scalability features
As information over the Internet becomes more and more revolved around communities and as the need for fast, dynamic content increases, simple caching can't do it anymore. In order to really stand out, a new application logic layer, which would interface with the database abstraction layer and provide tools for easy database sharding would be great. The idea is to be able to split data across several tables, but at the same time keep the caching features and the code intact(meaning that in order to use sharding features, one would only have to plot some rules for the data logic and that's it, no need to redo parts of the code or anything). The idea is inspired by the hibernate sharding feature, and by the ever increasing need for scalability.
Later edit: The nicest thing about sharding is that you can have parts of the data in different databases, spread across multiple servers.
