Some hints from Ray Ozzie this week on the future overlap between Groove and SharePoint:
"You asked if Groove is the future UI of SharePoint. I might ask the same thing, is SharePoint the future UI of Groove"
Microsoft will increase the connections between SharePoint and Groove by tying together specific functions of the user interface in the two products that are designed to work seamlessly with one another, Ozzie said.
"[SharePoint and Groove] are very, very complementary, and you will see in [Office] 14 and beyond increasing association with the things that you can do in SharePoint, and the things that you can do with Groove and the client"