I'm stating this from the perspective of how much (little) useful life may be left in the Slim if you are in the habit playing the latest games.
The way I see it the Slim was only thrown onto the market to compete with the Xbox One S in terms of price for the holiday shopping season (why anybody would spend any money on an Xbox One S after the announcement of Project Scorpio especially if they already owned an Xbox One is beyond me). As far as PlayStation/Sony is concerned the PS4 Pro is now the "current" console - basically:
- PS4 (Slim) - PSN Box Mk.I
- PS4 Pro - PSN Box Mk.II
- ??? - PSN Box Mk.III
PSN Box Mk.III may become necessary if Project Scorpio becomes too much of a threat to the PS4 Pro - it is just a possibility, ultimately Scorpio may not live up to the hype and in its current financial state Sony would not want to push forward at an accelerated pace. But there is the real "danger" that console generations have now become a phenomenon of the past.
While currently PlayStation is scaling back PlayStation Now
for a variety of reasons (streaming challenges for games, lack of net neutrality, etc.), Xbox is launching Xbox Game Pass which gives you subscription access to an entire library of downloadable games. This business model could become the (non-streaming) mainstream gaming equivalent of Netflix. If this is successful neither Xbox nor PlayStation will want deal with the disruptive nature of console launches anymore where they have to rebuild the game library from the ground up (conventional backward compatibility tends to make the hardware more expensive and/or require significant R&D into porting and emulation solutions) - so they will opt for successive performance enhancing hardware iterations of the same base architecture (basically a PC with a severely constrained range of components).
No, I don't like the way this is going - because I believe that in the long run once the majority of games are consumed via subscriptions, quality of new releases is going to suffer.