Not sure if there is still new innovation that can draw the interest of players.
Perhaps there is one, but still it boils down as how it is going to attract slot players because playing them is just basic, you just have to understand how it works and what is the draw line and what characters will be the bonus for a particular game. So it's hard to reinvent the wheel for slot machines because we have seen them all.
Most players are seeking simplicity and games without too many complications and I guess that's the edge of the slot. Players are contented with it because of the basics of the game. They could make a simple innovation that could make it more exciting but changing the whole game could only make it too complex.
Agree i think only themes could be change in slots like the colours the images but the rules and how simple the game to be played should be retained since thats the most people addicted. Makin it complex makes everyone not to play on it since it was new unless they want to try and if so they get addicted to the new and improved slot game