Who are the experts you are talking about, what ever may be the situation, it is really hard to accurately estimate the number of bitcoin address in existence, presumably there are about thirty million active users in the entire market and i am not sure how you can evaluate the amount of wallets in existence and even if the entire billion population starts creating address we will still have more of them available and if there is an address collision we will have a solution for that too with longer bit number, but you cannot compare it with the sands and dusts and from next time onwards, reveal the name of the experts.