Sony probably doesn't have anything to do even if MS outsells them again in December (which is looking very likely right now). At best, it looks like MS might come close to nullifying the gap (as in within 100 - 200k of it), but in that process MS is burning a ton of cash while Sony is making some. Then, the rest of the year is wide open to grow that gap right back up. We are talking about MS home backyard here, their own turf.
What I could see I guess is a $50 price drop between Feb (The Order), March (Bloodborne), April (Until Dawn?), May (new Ratchet?) and June (MGS V TPP?) 2015, before E3, IF they feel they have to maintain the momentum that way
It's sometimes a bit frustrating to try and figure out wth they're doing, but Sony's strategy is worldwide, and not dictated by the US/UK combo, as big as they are.