Actually... the grand scheme looks like this:

Win 95, 95, NT 4.0 and CE names remain the same... (that's a fact that will
not change)

Windows 2000 Professional is NT 5.0 Workstation... (also a fact due to the
announcement)

The merge will probably occur within a Service Pack for Window 2000
Professional... (pure speculation on the part of the people who test this
stuff and have seen the progressive migrations, and who have seen NT 5.0)

Note that one migrates to Windows 98, their registry format changes and is
completely rewritten.  This is part of the merge, which was the plan all
along.  Windows 9x and Windows NTWS would merge into "Windows".  The
registry format of Win2KPro (hey, I like that abbreviation :) and Win98 are
not identical yet, and they aren't going to be for the foreseeable future ;)

Best,
Joe