Sony will for sure be using Blu-Ray on the PS4
Nintendo, I think will go towards using HD-DVD's. Blu Ray has been on the market for like 3 years and even though the price of a blu ray player is dropping, I dont Nintendo will try to sell a new system with Blu Ray cause it could make the system expensive for customers. Nintendo strikes me as a company who always offer great or afforable prices on systems. It could be cheaper to develop a console around a format that has died out from being a huge media format sold in stores. What the price of an HD-DVD player anyways? 90 bucks? Amazon has been selling the 360 HD-DVD drive for about $90.
Microsoft: They would be stupid to not go with HD-DVD. I dont think HD-DVD will be used in the Xbox 3 cause Microsoft doesnt have faith in HD-DVD. They looked at HD-DVD as just for media and it failed. I dont think Microsoft will look at HD-DVD as a storage for gaming. Something tells me they are going the digital route on the Xbox 3.
