I know this seems like a controversial prediction because PS4 is dominating the sales charts, but hear me out before you gather your pitchforks and gutting materials.
Right now, the PS4 is appealing to all the casual gamers, be we know how untrusty the casual market is. They never stick to the brand for the long haul. So we cannot just assume Sony is going to hang on to the casual market. We can also see where Sony's focus is moving forward. If you look at PS+, it is how they are modeling their future. The PS5 will be built around this idea of renting your games to your box. Now I know this idea doesnt sound particularly appealing to most of us around here because it takes away even more control from the consumer and transfers it to the company. I know I am not the only one who is tired of that kind of attitude in the gaming industry, and just how gamers revolted against Microsoft when they tried that stuff, they will revolt against Sony too, which is going to cause problems for them.
Last but not least, the market crash of 2020. As a result of these tactics by Sony (and Microsoft more than likely), along with the fact that all these smaller companies getsucked up into bigger companies like the evil EA and Activision who do nothing but innovate and create new ways to rip consumers off, the industry will not be able to handle it, and in 2020, it will come crumbling down. Another blow to the sales of the PS5. The industry will crash, and the only company that will be able to withstand this is Nintendo, standing strong with their iconic franchises who will once again rebuild from the ground up. Nintendo has already proven that they can be quite profitable on 20-30 million sales. They can remain profitable despite what Sony or Micorosoft, or these giant publishers do. Everything can crumble around them, and there will still be enough people willing to buy Nintendo's 7th console that iwll allow them to be profitable.
The writing is on the wall with this one. You guys can bump it in 5 years, and we will all laugh at how crazy everyone will say I am.