There will be more Tier9 gems (and nothing higher). Toxic shock is the first of the meta tier gems, but there'll be others. The idea is that Merlin left behind the blueprints for gems he was making; Albert will help you construct them. They do things like flip your shields to rage, double your poison damage, turn any ice damage on an enemy into fire damage, etc.
Apart from that, you should be getting the next tier 9 gem early in Act VIII.
Apart from that, you should be getting the next tier 9 gem early in Act VIII.