While the idea of an add-on communications unit to allow for some form of wireless communication is interesting I think it would be detrimental to Sony to do it. Obviously, if done it would need to be PRS-505 compatible (let's consider the PRS-500 dead and buried for the sake of arguments). It would be safe to assume that Sony is well into, if not nearing the end, of the development cycle for the next generation reader. It's assumed that the new "communication add-on device" capabilities would be built into the new reader. Worst case is that a communication device would be built FOR the new reader and be compatible with the 505. Either way an add-on device like this would fly in the face of "portability" as you would need to carry it with you in order to have it available for use. Not to mention also needing to now carry your power cord more often as said device would undoubtedly be a power hog. Add to that that Sony would be creating yet another product team for a small portion of their business.
With the holiday season coming up I think that if we see anything device related I think it'll be a full on next generation and not an add-on. Sony will want to capitalize on the holidays and geeks are notorious for adopting early.
