To answer the OP's question, the answer is yes.
It is inevitable that computers start shipping without proper disk drives. The real question is "when"? I don't know when. Nobody knows when it'll happen. However, I doubt Apple is going to continue to release the MBP in its current form factor for too much longer. The biggest issue may be SSD storage capacity, and/or SSD supply issues, and/or the cost of the higher capacity SSD drives, rather than a lack of desire to release such products tomorrow.
Also, what gets released may not be called a 15" MBA, but a 15" MBP. Maybe it'll be a uniform thickness throughout rather than use a tapered design (e.g. ~0.68", which is the max thickness of the current MBAs), which may allow for a faster processor and also a much larger battery to be used in the system.
All we can do is guess.