There have been comments in a couple of recent articles (for example, here and here) that state that WSE 2.0 implements WS-ReliableMessaging. Before everyone gets too excited, I have to say that these articles are not correct; WS-ReliableMessaging is not available in the WSE 2.0 release. It is, however, something that we're considering for WSE 3.0.
I've been asked by people both inside and outside Microsoft whether WSE will implement WS-ReliableMessaging. This will not be happening for the 2.0 release, but we hear you loud and clear: WS-RM, along with Attachments work, is one of the top contenders for the next release (please, don't bother asking me for dates).
As Becky notes, I've already made some changes in preparation for alternative attachment models and we're doing similar thinking for other areas. This, along with interoperability work, is why the final 2.0 release is taking so long to close down.