I really don't see any good candidates for replacement at the moment.
Sure there are several games that in MY opinion are way better games. Rotation, even 8 ball (Chinese or other). Naturally I like straight pool the best, but it's time has come and gone as the main game. That is not to say it's at all realistic that the public or broadcasters will take to any of these games. People on here, who have been hanging around in pool halls for an unhealthy amount of time and inhaled enough chalk dust and cigarette smoke to kill an elephant, somehow think they know what people want.
Unfortunately, or probably fortunately, most people have not had their brains corrupted in such a dramatic fashion as to be completely desensitized to extreme boredom and completely blasè to all the actual charms of pool. These pool hall dwellers think a 2-4 hour one pocket wedge game on a table with 2.75 inch pockets will turn the world onto pool. No power shots, no jumps, no masses and pretty much no ball pocketing of anyting but hangers. No power breaks either, of course. Should anyone pocket a ball on the break, by all means the rules should discourage or outlaw a runout. I seriously do not know why these people don't play Billiards rather than pool and with maces to ensure their brains do not get overloaded with excitement. Personally the rules these people are pitching makes a proposal for a world championship of philately sound like an adrenalin explosion. To please these people, any event must be played in a mortuary-like setting with complete silence from spectators as well as commentators.Good luck selling this kind of game to any sane production company.
Its very hard to come up with a premise for a game that is both simple to understand and challenging. Most "newly created games" fall into the trap of being overly complex. I think a new game may come, but it will not likely be a refinement of 9 ball, because everything has been tried with that game, more or less. It's an elegant rule set for a game, but it is also a little bit limiting. The 9 balls do not leave enough to work with as far as refining, and the diamond rack has been competely mapped out to the point of being a joke.