It is really impossible to tell. Who knows what happens between now and October. Microsoft can announce a price drop, new games, etc. that might close the gap. On the other hand, Sony indeed enjoys advertising deals for big multiplatform games like Watch_Dogs and Destiny which may draw in new customers. Additionally, Sony might still have 'The Last of Us: Definitive Edition' and #DRIVECLUB this summer.Can't really see the gap being 400K+ before the Fall. The multiplats that are coming are well known as being multiplats on both last gen and current gen consoles. I feel that exclusive games are what's going to make the gap change and those won't be coming until the Fall -- or, at least multiplats that are XB1/PS4 only.
It's really impossible to tell what is going to happen next, as there are so many variables in play.