Well, if some horrible fate befell my 505, I'd just get it replaced under warranty
But assuming for the moment that wasn't an option, I guess I would wait a couple of months to see if there was a new offering from Amazon (Kindle 2.0, anyone?) and then decide.
I had a Kindle for a few weeks, and would consider another, better Kindle model that addressed some of my previous concerns...but if that wasn't forthcoming, I'd definitely buy another 505.