Neither does the author of the article.
> As far as the possibility of intelligence being intractable, what are the chances of this.
I think the odds are very good. Every known complex system -- the weather, for example, or an ant colony -- is intractable, let alone the human brain.
> Should we stop researching AIG because of the possibility that it might be too much for us to handle?
Intractability doesn't mean it's too much for us to handle. We can simulate intractable processes, and we do it all the time (that's how the weatherman knows if it's going to rain tomorrow), so of course it can be studied. The problem with intractable processes is not that they can't be artificially created, but they can't be artificially controlled (or predicted) beyond very short time frame. So it's very possible we could build an AGI, but won't know how to make it any smarter than us.
Make it as smart as the smartest of us and then it'll figure out how to become smarter on its own. Then ask it to explain to us how we work.
Tongue in cheek but once almost-as-intelligent-as-a-human level is reached the next step is not that far fetched - quantity, multiple times faster than humans learning and we have progression on a different scale. Or we can always try mutating the thing to see what comes out - crude but worked at least once.
But this doesn't necessarily follow. The experience of a mind working at a higher speed will be a slowing down of time -- imagine what you'd do if time slowed down. The machine will not necessarily learn more (we might have a limit of how much we can learn), and will probably experience boredom and frustration (as everything around it will be slow) that might drive it crazy.
But most AIG researchers don't throw their hands up and say, "Oh damn, it's impossible (intractable), it's magic because we don't understand." Forgive me if I feel this a less-than-useful sentiment.
As far as the possibility of intelligence being intractable, what are the chances of this. Is it likely? If we don't even know what AIG entails, how would we possibly put odds on this? If we don't have the odds, what use is there is thinking about it? Should we stop researching AIG because of the possibility that it might be too much for us to handle?