The lost legacy is dlc for uncharted 4 sold in the season pass or as a standalone. 

I could sit here and argue with you on this ... but I think it's very complicated and we don't really know, although my guess would be that you aren't right about your minimum of four years. 

I still agree with your basic premise that, games are taking longer to make to some extent.

Doesn't seem tough to me. Cross platform should be the way to go. BOTW did this quite successfully. Sony is notorious for being slow to bring 1st IP games to new consoles due their support for the old consoles. This would solve that problem.

They would make it an exclusive but it be cross-gen. Duh.

Well take into account kingdom hearts 3 announced in 2013. Supposedly coming this year. 5 years from announcing to release. 

Death stranding: Announcement in 2016. Two years on and still no gameplay. 

FFVII remake. Announce 2015. Still no release in sight nor new trailer since. 

The last of us 2. Announced December 2016. Probably a 2019 game at this point. Which will make it release six years after the first one. 

Crackdown 3. Announced 2014!. Still not out. 4 years! Since announced. 

Yes, games are taking forever to make these days and only getting longer. Outside of your yearly sports games, there are very few devs left who can get more than one installment of a particular franchise out in a single gen now. The recent Tomb raider games comes to mind who has a third coming soon. So congrats to them. 

Do what they did with the original God of War 2: make it the swan song for the system. That game came out a year after the PS3 on PS2 only.

That is most likely the case, but I think it would be awesome, if Sony took a new approach to things.

Why not work on building an ecosystem where people can upgrade at their own pace? Allow the core players to grab the PS5 for their 4K/60 gaming desires, while those that want a $100 entry price, and will hold on to their 1080p or 720p till the last straw, can still drop $60 on that new peice of software. 

At the end of the day the hardware is just a means to sell software. PS5 does not have to explode out of the gate, if the PS Ecosystem is strong a vibrant. Having a pool of 200 Million users between say PS4, PS4 Pro, PS4 Portable, and PS5 would be much better, and make much more, long term and short term, than having a pool of 6 - 16 Million PS5 gamers. 

If all PlayStation products share the X86 and Radeon tech, then supporting them all, will be a very low cost endeavor. If they can Sell for example 15 Million copies of GOW2 on the PlayStation Ecosystem, but only 7 Million by restricting it to PS5, why would they not spend the small amount of extra time and man power, to more than double their return?

I understand why they could not use this type of business model in the past due to PS1, PS2, PS3, PSP, and PS Vita being vastly different devices. If that won't be the case going forward, I don't see any advantage in following this hail mary approach. Might as well keep all of your users as long as possible. Make the ecosystem as healthy as possible. Build in the most value on the market. Work to keep your consumers buying devices, because they want to, not because you force them to upgrade.