Delays are nothing to worry about. We have too many examples of rushed games, or games that were shipped as less than an ideal value. Titanfall with no SP campaign, The Order with zero MP (and short). Buggy crappiles like AC:U and Halo MCC (thankfully both are much better than on release today).
3rd party titles will dominate this holiday for X1 and PS4 anyway in totality. If PS4 tries to stay at $349 or higher for the price for Nov/Dec, then X1 will again win that period. If PS4 drops to $299 like past PS consoles have targeted, then PS has a solid chance at winning, depending on what the MS specials would be. I think that a $349 PS4 would have to combat a $299 X1. But a $299 PS4? I think even a $249 X1 would lose. The barrier of $300 is a HUGE mental one that opens the door to the mass market.
As we see from cheaper X1 losing to $399 PS4, the PS4 has the higher base demand and mindshare, but that can be busted by a good enough deal, as we saw in holiday 2014. Sony isn't dumb though, their sales for holiday 2014 @ $399 were very solid. But I don't think a $399 console will do well this holiday. The masses simply can't or won't spend that kind of money on a console.
So :
First to $299 will have a huge impact. Huge.
PS4 at $299 will blow minds. X1 at $299 or less should do gangbusters too.
The second part of this will be really notable in 2016. As 7th gen software sales continue to tail off, when the big multiplat releases drop off and no longer get 7th gen ports, 8th gen console sales of $300 and less will be massive. I think that it's conceivable that 2016 console sales for 8th gen could be peak years for both. Previously there wasn't NEARLY as much cross-gen. Take 6th gen to 7th gen for example. Most 360 titles were 360 only. Ditto the big PS3 games. If you wanted good new releases of major franchise stuff, you were almost forced into PS360ii. PS2 had the longest trailoff, but beyond sports titles there wasn't a whole lot there vs PS3. Gamecube and OGBox basically died a rough death upon release of their successors.
So I imagine there are gobs of millions of users out there just happily eating up 7th gen releases to this very day because they don't feel the need to buy a new console yet. Many of these millions only just bought in the late years of gen7 anyway. So it's hard to have paid $299ish for a PS3 slim or 360, and then turn around and pay even more for a gen8 box this soon.
Bet on 2016 being bananas huge. Biggest console sales year of all time imho. Remember, Japan should be heating up that year too, finally bringing the big franchises they want online in decent numbers.