Welcome to MobileRead, Marinerrr!
All the device vendors are out of stock off and on lately, they're not all bringing out new models, in fact three of them only launched their current models within the last five months. The PRS-505 was launched in October of '07 -- I wouldn't look for a new model before October '08 (at the
very earliest), and that's only if they decide that they've come up with enough new tricks to warrant a new model that quickly.
The reason that these things are so hard to get is that the display panels are all made by a single company, PVI, and PVI has been having trouble keeping up with demand for them. There's really not anything more to it than that.
