I was almost positive that there was a post to the mailing list within the last 4 months that strongly implied — or outright stated — that there’d at least be a beta by summer 2009, but I haven’t been able to dig it up, so I’m not sure.
To be honest, I’m not really that concerned about TextMate. Sure, I’d love to see it, because new stuff is always cool; but in my opinion there are only 2 big features missing from TextMate — split-pane viewing and better undo support — and I’ve found I can live without those. TextMate 2 will probably be awesome, but the current TextMate is such a great editor that I’m not anxious for TM2 to come out.
Update: A public alpha is due out by Christmas 2011.
Update: A public alpha is now available