More are planned, but that will just make them more varied, not more frequent, as you say. Right now there are six or seven, we plan to double that or more. Pablo's time is rather limited at the moment, but he's got a big list of them as well as the other things on his plate (sound effect upgrades, etc).
The AI taunts should presently always be effective, you might just not be realizing what it is really taunting you about in some cases. It doesn't taunt you when sending waves against you, but it will taunt you if you lost a lot of ships on its planet, it did not, and then you withdraw your ships to defend against that wave.