Well we can see a lot of ICOs related to poker. I think we will see a huge increase of poker rooms soon. However, I am not sure, but it looks that online poker is slowly losing its popularity, so maybe there isn't many interest in opening such sites/platforms. But after all, it's only my personal opinion.
I really doubt that we'll see any popular Bitcoin poker rooms popping up any time soon, the popularity of poker in general has been going down for a couple of years now.
Combine that with the fact that there's only one really popular platform and it makes sense that no-one is willing to invest in opening up a poker website in Bitcoin.
I'm also thinking that it's way easier and more profitable to just set-up a regular casino. You don't tend to make much money from the rake as a casino, especially not if you don't have too many active players.
I'm sure Pokerstars makes quite a lot, but they are the largest.
It's going down also because of no place to play poker with our bitcoins here. I'm pretty sure when we got a huge big bitcoin poker sites, many people will back gambling on poker and gather on that bitcoin poker site. Maybe we will got that a big bitcoin poker site in the future.