I am happy to tell you that version 5.1 of Sitefinity support extensions in your urls. Check out the release notes: release notes
. If you need additional information about that, feel free to ask.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items