Within reason, sure, but by the same token, the x series are resulting in the EOL'ing of the BMW 3 wagon in the US marketplace in the 2013 Model Year...
Overall, we do have to also recognize that the fragmenting a product line into smaller subsets does hinder manufacturing economies of scale, because even if variable costs don't increase, the fixed costs (which need to get amortized) will figuratively double, thereby making both products more expensive to the consumer. This isn't canibalization per se, but it is related: the splitting of a product line has to attract more buyers - - while not canabalizing itself - - in order to get back to what its margins were beforehand; basically, its a "Grow, Or Die" paradigm.
Apple's lines for the past decade have been pretty sparse...but that's IMO still a survival-based reaction to the '90s and the gazillion permutations of Performas and PowerMacs that caused customer confusion and higher manufacturing costs ... a clear lose-lose strategy.
The good news in this area is that total Mac sales YoY continue to grow, so this makes additional product variations less expensive and thus moderately more likely.
But the bad news is that we (the public) don't have very good data on if this is a "Rising Tide Lifts All Boats" that has also improved Mac Pro sales too, or if the growth in Mac sales has been primarily limited to just a few specific models.
For example, my personal recollections of yesterday's call mentioned ... MBA's and iMac's ..?.. as worth mentioning for doing well. We simply don't know how/if Mac Pro sales are doing relative to the whole, although since laptops are reportedly 70+%, we do know that the desktops aren't a big piece of the pie, even on just the Mac-only side of the business.
-hh