First, Justin, we'd love to have any help you can provide during Oneiric's development!
Its important to note the change means very little in terms of the mechanics of Ubuntu Server. In addition to this direction, a decision was made at UDS to drop all of the cloud components, and in fact, most of the "extra" server packages, from the Ubuntu Server CD ISO (the DVD image will still have everything). They will still be fully supported, but not shipped on the CD or available in the installer. Given that, the only thing that the OpenStack change means, is that anything we develop around private IaaS solutions, will focus on OpenStack.
Eucalyptus is still available, and will remain available as long as it meets the requirements for Ubuntu to keep supporting it. Eucalyptus, the company, has committed to bring 3.0 into Oneiric, which will bring with it the open sourcing of some features that were previously only available in their enterprise edition.
If you're going to be deploying something that you expect to live for more than 18 months (the supported lifetime of 11.04 and 11.10), I'd suggest using 10.04 as your platform, as it will receive security fixes until April of 2015. To contrast this, 11.10 will reach EOL in April of 2013. Likewise, unless you want to patch OpenStack yourself, you might want to consider Eucalyptus running on top of 10.04.