I've been reading 'Peak', by Anders Ericsson and Robert Pool, and for its sources it uses various studies where, through practicing some task, people have enlarged various regions of their brains and became capable impressive tasks. One example is Einstein with his enlarged region of the parietal lobe , which he has in common with other mathematicians. Another example is the enlarged posterior hippocampus of London taxi drivers .
However, the posterior hippocampus isn't part of the neocortex. Also, those taxi drivers, after successfully memorizing the entire layout of London, performed worse than average at other spatial tasks.
I was going to compare other species with similar numbers of neurons in their neocortex as humans (around 20 billion), but I can't really say whether they're smarter or not in every way. It looks like all species with a similar number of neurons are highly social. Also, crows seems highly social and show the ability to use tools, but they use an enlarged Nidopallium which displays similar functionality to the neocortex.[4, 5]
We can't really know that perfectly. That's the point of science: to figure out what we don't yet know.
I can take a guess though: I'd say we'd have machines better at complex animal tasks like underactuated movement, speech comprehension, object/text relations (like cortical.io), etc. However, I don't believe we'd end up with anything that takes action without studying other regions of the brain or linking our virtual neocortexes with AI.
Isn't that what we do already? Do you mean it'd be, 'actually able to predict the future like an oracle'? Or do you mean it'd, 'look like it was predicting the future while in actuality using logic and observations that people wouldn't normally use to come to its conclusions, like Sherlock Holmes'? If it's the first, then no. If it's the second, sure.
Hope that helps your curiosity a bit. Keep in mind that I've just been studying this for a while too. I haven't experimented with or made any working HTM implementations yet.