My guess would be that the next update of the MBA would be a HDD of 120 GB. If that update is to come soon - such as this autumn - then I doubt we'll see the upgrade in the SSD that some posters here have hoped for, as competitively priced SSD drives at that capacity are not yet available. It may take another year for the capacity and the price to make the addition of larger SSD drives to the MBA feasible. Yes, I agree it would be wonderful to see now, but I doubt we'll see it.
Cheers