They could keep with Ps4 knowing all 3rd parties will be on ps4 this will put immense pressure on nextbox imo if nextbox doesn't take off in the face of Ps4 then that's the final nail for xbox as a home console 

It's not very wise to give your main competitor a large headstart, it's one of the things that allowed 360 to take off.

PS4 would definitely continue to sell very well and get most 3rd party titles but PS5 could potentially suffer if its gives XB4 a 1-2 year headstart.

I could see PS giving MS a year lead at the absolute most. If XB were to launch the entry model late 2019 at say 6TF, and planned to launch the top tier model late 2020, PS could potentially want to wait until late 2020 as well. In this scenario or just in general, I would think PS would prefer to launch in the same month or no later than 6 months after a next gen XB, especially if there's a higher end XB coming not too long after the PS5. Depends on the PS5 specs and price point.

The main reason I potentially see PS4 holding it's own for an entire year with a new XB on the market is that PS5 will be X86 just like PS4 and unlike the PS2 to PS3 transition. It will very likely be BC with at least the PS4, with a likely price of $399-$499, unlike the PS3's $499-$599 price point. XB would not gain anywhere near the same lead as they did with the 360 this time around.

I still think PS would rather not wait an entire year if they don't have to though.

I'm amazed at the PS4's performance.

And I'm kinda thinking similar to another post here about how Sony is in a unique spot with the continued success of PS4 and potentially looking at the last time they had a super successful platform and how things went following that.

PS2 was a beast and the PS3 had several troubles in it's first 2 years on the market. I wish I was sitting in those meetings while they are hammering out the details of the transition from PS4 to PS5.

I hope they just keep it safe. Just keep rolling out great games and a 'boring' successor to ps4.