The PS4 might be outselling the competition, elevating the PlayStation brand with a slew of exclusives past generations' libraries never came close to... but there's still the PS5 to think about.
Besides having a logo that'll sell itself, the PS5 is poised to actually be the "last" PlayStation you'll ever buy. The gaming industry is overall moving into full digital distribution (just look at 2018's digital vs physical sales figures), and there are many rumours floating around that PlayStation and Xbox will turn into "platforms" of content distribution, rather than a hardware/software combo. Think apps like Netflix being accessible across TV and phones alike.
We've seen Sony experiment in this way with PlayStation TV; a set-top box-with-a-Dualshock 4 combo that lets you play everything from PS1 classics to PS Vita gems, all without a bulky console taking up space. Sadly, the PlayStation TV has since been discontinued, but going forward, you have to imagine Sony are taking influence from the PS4's meteoric success, and what the competition did right and wrong.
Where they can innovate is still up for debate, but there's a LOT fans and consumers have been demanding - in some cases - since the launch of the PS4...