There was a time when I thought it would be cool to see another competitor enter the video game hardware market and compete with Sony, Microsoft and Nintendo. The ones that always came to mind was Samsung or a big publisher like Electronic Arts, Bandai Namco etc. But this seems impossible because in order to compete with the big three, you pretty much need to wow the hardcore gamer with impressive graphics, an impressive first-party lineup, and a lower price (if not a similar price with more compelling features and content). And as much as it would be interesting to see what a brand new platform from a different company would look like, whether or not the graphics would be any better than what we're currently seeing, what first-party games would be on display to wow gamers, it still means a huge investment that probably wouldn't really change the face of the video game hardware market dominated by the big three.
"What if one of them exits the hardware market?" I don't actually think that will happen. Nintendo have been around the block the longest and, with the exception of the Wii U, they continue to successfully market and sell their consoles like hot cakes. PlayStation consoles have also been very successful for Sony that they were able to take a serious venture into VR gaming alongside the PS4 and PS5. We've even seen some of their notable exclusives make their way to Steam such as Horizon: Zero Dawn and Death Stranding long after releasing on the PS4, making them even more money and creating more fans. And although Xbox is relatively new, compared to Nintendo and PlayStation, Microsoft have been acquiring/creating studios to what I believe will ultimately bolster their first-party lineup and they also offer a cheaper, easy way to play through their GamePass service. Also, the Xbox Series X was reportedly their biggest launch ever so definitely the Xbox brand is doing well, as is PlayStation and Nintendo. The current gaming landscape carved out by the big three is interesting enough. They all just need to bring back some older great exclusives or develop spiritual successors to them to sweeten the deal. But I don't see any of them in danger of losing, let alone being threatened by a newcomer. They're just too big.