Lotus Notes XPages for design and Oracle (or other RDBMS) for data
There actually has been native support for RDBMS/JDBC connectivity in Xpages since July 2011. Take a look at the Extension Library on OpenNTF (http://extlib.openntf.org/) and read the blogpost announcing the functionality: http://www.openntf.org/blogs/openntf.nsf/d6plinks/NHEF-8JYMXE.
It's not yet officially supported through IBM (not part of the Upgrade Pack 1 - http://www-01.ibm.com/software/lotus/notesanddomino/nd85-UpgradePack853-1.html), but there will be support for it in the future.
The short answer appears to be "yes but no" .
XPages is JDBC compliant, so you can connect to anything, including Oracle. The snag is, you'll probably have to write the code yourself. Apparently there are plans to open source a JDBC-based Relational Database XPages DataSource but there's been no activity as such. Find out more
XPages101.net may be a good site for cutting your teeth on Xpages. They have 60 lessons you can subscribe to. They are highly recommended. You may be particularly interested in lesson 55.
DISCLAIMER: I am not affiliated with XPages101.net in any way.