I think for me it will be when there is a good list of discounted/pre-owned games at low prices, the firmware has been updated so the blu-ray player and media features work well and also ideally the bring in the ps1 and ps2 compatibility Sony has mentioned.
Ultimately it will be dictated by price and perhaps a bundle.
At the moment I still have a huge amount of ps3, 360, PC and wii u games to play through so the PS4 needs to have games that will go to the top of that games list.
I expect to buy a ps4 late this year, early next realistically.








