How long does it take to earn a black belt in Karate?  
I don't know, but I do know that Karate was taught in Japan after the Taisho era
Is Karate an offensive or defensive art?
Not sure, but I do know that full contact karate comes in different formats
In your opinion, would modern Karate me comparable to its ancient counterpart?
Yes, especially when you consider American Karate as a generic term
That's interesting.  In light of modern MMA fighting, does Karate remain a dominant art form?
MMA seems to be more of a mix of other combat sports