I am not sure. I don't know if they have a plan to add new currency in near future. As udidrone already said, They are in the market for over 3 years now. and there were no significant changes in payment gateways/methods. Yep, LTC is cool when it comes to fees compared to BTC and ETH. ETH was ridiculous for the last two years.
Another thing is, I don't think they are going to add an internal exchanger in near future. Every casino has its own business strategy. We don't know what is their strategy but not having internal exchanger benefits the casino. I guess you got the point. I guess Adding Doge and TRX would be awesome. They will get a lot of players from the community since the fees are cool.