They're still developing the game, there's going to be one more release called ESF: Final. This is going to contain better graphics, better physics, huge maps, more characters / attacks, and an overhaul of the melee and beam systems.
I think people were probably talking about the Open Betas not being made anymore. It's slightly confusing, but basically, ESF 1.2.3 was the last stable version of the game which was released, but it's very old now. A few years after they released 1.2.3 they started releasing the open betas, which were basically weekly updates of the game. These are all unfinished / not very playable, but they were intended to give people some idea of where the game was at that stage in development. So that's that.