I agree. The increasing length of the Mac upgrade cycles has Apple users very frustrated.
But Apple’s silence is well thought out and intentional. They could easily leak news of an upgrade to quiet the critics – but that kills sales of existing inventory. And Apple’s bigger game plan is to slowly phase out desktops and then laptops in favour of more mobile devices (iPad and iPhone). I don’t like it either but so far they’ve done a good job of leading us in the right direction. We’ll find out together :)