The word of a VERY experienced mod with over 10,000 posts and almost 2 1/2 years on the forums isn't enough? As NJB said there is no user "replaceable" chip inside a BB.
It would cost him more than it's worth to have someone even try it, let alone find the memory to replace it with, and it probably wouldn't work anyway, and most likely fry the BB in the process. Even if it didn't fry the BB, new code would have to be written for the extra memory to be recognized, and the only people that can do that are RIM.
If you read about the Pearl, 2Gb cards wouldn't work in the initial release of the OS. We had to wait for an OS update before we could use anything bigger than a 1Gb card.