* Will Assistant be world-changing?*
No. But it will probably be a damn good feature.
Will it address foreign languages/cultures
Probably, since Nuance can do a fairly impressive number of languages and all signs is Apple is partnering with them.
relationship questions
No. God no.
open task API
Maybe, but I would be a little surprised.
payments
Now we are just throwing buzz words together. Want to know why the "speech to text world" is "untapped"? Cause it is made up. Plus it would essentially be either a search ad or affiliate marketing situation, neither of which seem very Apple-like.
Facebook social knowledge
Again, doubtful. I mean, they've gone out of their way to integrate Twitter in iOS 5, which reeks of Facebook and Apple not coming to terms. But maybe they banged out a last minute deal.
I am sure Assistant be like most Apple features. Fairly impressive, a bit more detail oriented than the competition, but ultimately not that much better. If anything, I think it will be the new Facetime. Good demo, good for ads, some people will use it a bunch, but mostly a showy feature that will get used once and then ignored by the vast majority of users.