There's already a thread running on this on one of the other boards:
Also, someone in that thread links to a statement on the matter on the Pegasus Mail website.
It sounds unlikely right now. FWIW, if you'll be using the GNOME desktop I find Evolution to be fine, and more stable than it used to be. It's not likely to be lacking features you might want--although it may have too many for some tastes, since it's a full-blown PIM. The standard KDE mailer is fine, too--although again they followed the PIM model, and it's a bit cumbersome. If a PIM is more than you want, I hear very good things about Claws Mail. There's a nice run-through of MUAs for Linux in this podcast:
Some people have got Pegasus Mail to run under Wine, as you'll see from the thread I linked above. I haven't been particularly successful with that myself--I get frequent crashes, and for some reason Pegasus can't communicate with one of the mail servers I use when running under Wine. But you might like to give that a try.