Do you think that the Islamic State is an entity which will vanish in the future or not?

Define your time scale. "Future" is very very long, everything will vanish in time.

Do you think that their particularly violent brand of jihadism is a worse menace to the sanity waterline than say, other kind of religious movements, past or present?

No. I can't see why a particular brand of fundamentalist Islam is a worse menace than, say, Stalin or Mao.

Do you buy the idea that fundamentalism can be coupled with technological advancement, so that the future will presents us with Islamic AI's?

Coupled with technological advancement, yes, as to "Islamic AIs" I don't understand what does that mean.

Do you think that the very same idea of rationality can be the subject of existential risk?

The subject of existential risk is humanity. Are you asking whether rationality can become extinct? Not likely, for, as Richard Feynman noted, "Nature cannot be fooled".