Good luck with that one, you'll need it. People don't like feeling that they're being tricked, and this plot twist lends itself to tricks. BUT if you do it right, people will nod their heads and say, "Ah! Of course! I should have seen it all along."
In The Matrix, what is and isn't real are fundamental questions to the story. How you justify this is going to be very touchy. For example, the character isn't going to be transformed into a new person through a mere dream. I agree with Mary that you need some sort of established story element that makes the whole thing work. I'm not sure if this is magic, VR, or something along those lines, but it sounds like maybe you've already nailed down that part.
A mystery is a good example of where people are tricked by the author and like it. You create a situation where everyone KNOWS they are being tricked, and people are anticipating the plot twist, guessing who the real killer was and how it got covered up. People don't read a mystery novel and get shocked that there is a mystery.
So if you're going to make this work, you'll need to follow the mystery formula. Leave clues as to what is going on. Everyone can see SOMETHING is out of place, but the exact twist is eluding them. When the actual reveal takes place, the reader should go, "Wow, I didn't see that, but now that it's clear, it couldn't have been anything else."
You really need a plot twist to bring it home, so it's not following the total stereotype. Maybe the character can be angry and resentful of the manipulation carried out on him to push him into his achievement. Imagine Ender Wiggin from Ender's Game deciding to make the world pay for how he was manipulated and used to exterminate an entire species. IWAJAD is too pat of a solution, and SOMETHING has to make this unique and not just frustrating. Exactly what form that takes is up to you, but don't just leave it like that.
- EDIT: PS this is one of the few plot twists I have ever seen singled out by literary agents in their "DO NOT" lists, so it could be tricky to get published. If done right, it can still work, but I thought I should mention it.