It seems fairly clear Apple are waiting for the content deals to be signed before proceeding with a new machine and software. Apple aren't stupid - an ATV based around the A4 chip supporting 1080p output and running iTunes onboard (allowing streaming from NAS units and streaming/syncing to PCs/Macs/ipods etc) would absolutely clean up in the media streamer market. However, until the deals look like being finalised it doesn't really make sense to release new hardware tied to the existed software. If a new IphoneOS-based ATV came out I'd snap it up straight away and either sell the original or move it to the bedroom - after all, it's still good at what it does. And those ipad screens posted earlier would work just as well on a remote-driven device - they definitely have a 10' interface.
Sadly, until Fox, Warner, Sony, Universal and Paramount agree terms (lets face it, Disney will be on board) I don't think we'll see new hardware unless Intel or nVidia actually stop production of the Crofton or 7300Go chips.