Why would the 15" get the axe? It is an absolutely brilliant, large screened laptop, suited for heavy computational tasks on the go.
Is there actually a better 15" laptop right now? There might be some contention in the 13" category, but with its perfectly sharp retina display (I say "perfectly" because 3200x1800 is IMO of limited appeal / advantage despite being higher) it really has no competition right now.
The smaller 13" Retina Macbook Pro is a compromise between a non quad-core device and smaller screen for better portability and mid-range performance.
Frankly, it's more likely that the
Macbook Air would vanish; what's the point of the "Air" when the retina Macbook is
lighter than it?
Apple may have introduced the retina Macbook, but it is obviously in the non-Pro category with its comparatively weaker processor. I'm getting one, but to me it seems clear that it is targeted at the
personal segment. It is a
lifestyle computing device, even as the iPad is a
lifestyle media consumption device, and the

watch is clearly a
lifestyle wearable gadget. You could debate the continued success of these products, but I think the intents and target markets are undeniable.
You may argue ports and all, but Apple has always tried to eliminate that which is not strictly necessary, and more than 1 port, especially with ever improving wireless connectivity, is not
strictly necessary.
At some point in time, everything will be wireless - power, storage, inter-device data transfer. And I'm pretty sure Apple intends to lead in that direction.
In the meantime, "Pro" still needs significant connectivity - the 15", I am sure, is here to stay for a pretty long time....