Will Ikisithian armed force AI be smarter than current group trash AI encounters?
As much as I'd love too, its unlikely we are going to be changing any base AI greatly. No need to explain why that is a ton of work. I would be ready for some... surprises as far as raid boss abilities are concerned though...
How will the continuance of the Main Quest compare to, say, the scope the Vah quest?
The MQ is amazing and an important aspect of Ikisith. But TM did amazing work on the Vah quest, and the MQ is unlikely to reach that scope any time soon... that being said you won't be disappointed in where it goes.