Even if the Canon D450 is announced in January, don't expect it to be available right away.
As for the Olympus E-510
, I think you better read this
. This camera was announced in March 2007 and made available to the general public in June 2007.
Maybe the Canon 400D
would be your best choice, if you want to buy now? Since you can borrow good quality lenses by that brand, that's the one I'd suggest.
When you do decide, please make sure you go through the affiliate stores page
, to support Camera Labs.