I would also be interested in the answer to this question.
Actually, it appears that Lucene and Solr development is becoming more tightly integrated. It looks like they're still planning on maintaining separate products, but they're coordinating releases (I think). It appears that "trunk" is the 4.0 release, the first joint Solr/Lucene rollout, and it also appears that they're going to have spatial support…
Spatial support is a key, unaddressed ECM problem.
