The fact that Apple did not release new Macs and Mac software at the keynote does not mean there aren't announcements very near. We all know Leopard should come out in "Spring '07", so that's probably _not_ going to be the first week of February, and no it _doesn't_ depend on when the first flowers bloom.
Whether or not the _iMac_ is getting a quick update in the near future: Who knows. But I'd mainly think about the software here - and from what you write, it seems like you already do. Personally, I _would_ wait for Leopard and iLife and iWork versions to appear now.
The important thing to discern here is: Is it, right now, a definite *need* for a new computer or rather a *wish*. If it's more on the wish-side, the wait will be worth it.