From what I've read in MS chats and blogs, older collections and cases where
older collections types were used in the framework will either not be
replaced at all or will be slowly phased out(perhaps 6 years down the line,
regular collections may end up marked obsolete, maybe. But they would still
be left in the framework for a long time to come I'm sure.). Replacing those
classes would break a tremendous amount of code (read, 99% of existing code
base, where have you not used a collection?) and would take support for
basic collections away from languages that don't support generics which, for
a while anyway, will probably be more common than languages that do. Some
languages that a target the framework may never get access to them.
I would expect something more like System.Collections.Generic namespace with
generic collection classes, but until it comes out(or hits a late rc anyway)
no one is going to know for sure how it works.