8gb of Ram may be asking too much! You have to remember that the ram on the MBA is integrated into the motherboard... so it doesn't even have one "slot" right now. if it did, people would be upgrading to 4gb already (I know I would). 4gb is a realistic amount to build into the motherboard of the next gen, 8 would either take too much space (depending on how many chips have to be used, if not, see next), cost wayyy too much, or get too hot for use in the MBA.
It's using the space equivalent of two slots. I wouldn't predict 8 GB or two slots, but I would love LOVE LOVE it!