Pro: Must be updated, it's way too old and it hasn't given Apple a market share boost in a crowded marketplace.
Air: Must survive, it's Apple's most profitable notebook, it's form factor is still relevant, and it's the go-to for IT managers in scores of corporations whose junior and senior exec's want a Mac.
RMB: Still very new, still years ahead of its time, it's selling quite well, there is no rush or need to touch it until the Pro and Air have had their very important moment.
Pay attention to the stock market and pay attention to shareholder value, you'll have a better understanding of why the RMB is the lowest priority for Apple right now. A year ago to this day, Apple was trading at $130 a share. Today it's $96. That's a -26% drop. That's staggering. That's speculators deciding that the salad days of Apple are gone and growth is going to slow.
The iPhone isn't going to turn the company around any more, the Watch is ho-hum, TV lacks studio support, iPad is saturated. Notebooks can turn speculator perception around very quickly if Apple creates a compelling Pro and Air revision that makes people need to throw their old versions out and get new ones.
BJ