While not specifically mentioned on the tested operating systems list for this board. Am I likely to have any trouble upgrading from XP 64bit to Windows 7 64 bit?
If so, does Intel plan to offer support for Win7 64bit with the S5000XVN in the near future?
Hard to say, with unsupported OSes. Sometimes they install fine, sometimes they seem stable at first, but I wouldn't trust an unvalidated OS for any production work.
Given the age of the XVN, I seriously doubt it's on the roadmap for Windows 7 testing.