It's not impossible in principle, but: - we don't understand enough about the brain to emulate it. - we don't know how to model the brain. - even assuming we

It's not impossible in principle, but: - we don't understand enough about the brain to emulate it. - we don't know how to model the brain. - even assuming we had the required scientific knowledge, there would likely be major engineering problems. So, in other words, it's not impossible in the same sense FTL travel is not impossible, our scientific understanding does not categorically exclude it, but making predictions as to when it will happen is kind of silly, because it will likely require several fundamentally unpredictable scientific breakthroughs.