I am optimistically holding out for a 15" Macbook Air with 8GB RAM. Failing that within the next 6-9 months, my next Macbook will be the 13" Air
If that never happens, I'm just going to get an Optibay or equivalent.
the first company to release a 15" 1080p "ultrabook", whether it's apple or one of the windows manufacturers, will get my money.