Why can't I vote for Wii U to be in the lead? ;)
Hype will probably be slowing down for the PS4 and not many big games this fall versus Nintendo in their prime season with amiibo and Smash Bros. I'll say the PS4 will be 3-4million ahead, voting 3 as I think it'll be closer.
It's already 2m more being on the market for a year less. In Sept Sony will sell a ton more systems in that month alone. On Bf sony will sell a ton more systems in that day alone. In short, the gap will be closer to the higher end of the poll than lower end.