I don't know. New slot machine developments aren't just limited by technology, they are limited by regulation and the need for casinos to maximise their profitability over time. This puts a limit on the new features and user interaction they can offer. Perhaps they will be able to read a player's style and adjust the game to keep them playing for longer, or get them to pay in more without affecting the machine's overall odds, but I suspect regulation would quickly stamp that out.
The slot industry needs to do some serious adapting in order to entertain a generation that was weaned on Nintendos and Wiis. If they can't come up with ways of attracting and keeping the attention of the younger generation, then I think casinos will see a big decline in their revenue in the future.