All:
Actually, the official story is as follows.
In Fall 2005, "The Wall" will open on Broadway as a full-length musical. This required that Waters and Gilmour "play nicely in the sandbox" so that all the legal and financial details could be worked out. In having to "act nicely," Waters and Gilmour have "agreed to disagree" for the first time. And while there still seems to be little love lost between them, they are talking (and apparently not solely through lawyers) for the first time as a result of the launching of "The Wall on Broadway."
In this regard, it was actually Gilmour who made an overture (no pun intended) to Waters about a "reunion" - which would basically amount to Waters going on tour with Floyd, if not worldwide then at least in major cities.
If - and it is still a big if - this tour is worked out, the tour itself would not start until after the opening of "The Wall on Broadway" - i.e., in 2006. So, at the very earliest, Pink Floyd (with Roger Waters) would undertake a world tour in Spring or Summer of 2006.
I'll keep you informed of any further details I learn. Oh, and how do I know all this? All I can tell you is that I have an "in" on Gilmour's doings...
Peace.