Even though Ubuntu 11.04 has just been released few days ago, it doesn't mean that Ubuntu developer stopped working at the next release. In fact, they have started to work on Ubuntu 11.10 (Oneiric Ocelot). Their work can be seen by the availability of Oneiric repository at Ubuntu mirror site.
For now, the repository is not yet completed, as it's just few days since the stable release, but some work has been available, for example the inclusion of Linux Kernel 2.6.39-rc5 and probably newer GCC 4.6 and many more.
Remember that Ubuntu 11.10 is not yet suitable for daily usage. They haven't release Alpha version yet, so it's just a rough version, updated daily to improve the overal system of Ubuntu.