Well, from my perspective - there won't be any limits. What do I mean by that? Right now you can sell a blue partyhat for 6--M to 6--M gp, meaning the price difference isn't that much but after the limits have been lifted up, you can sell that blue partyhat for 5--M or 7--M. As time goes by, you will realize how much they will go for in grand exchange, what's a good price and what's bad.
So what's the point of grand exchange? Well, you don't have to go to World 2, and find a buyer for it - You can just let it sit in the grand exchange and do something else.
This is what I think, I don't know what they have stored for us.