They should just focus on the MacBook and the MacBook Pro. With the new 13" MacBook Pros, the weight and footprint is getting ever closer to the MacBook Air, so that's also an option.
This is the computer huge numbers of people want, but Apple force up the range to the entry level 13" MacBook Pro (which incidentally IIRC currently has the same TDP class CPUs as the existing Air...) to get a decent display.
Really the entry level 13 inch MacBook Pro should start at $999, given it largely _is_ a MacBook Air but with Retina display and TB3. Heck the 13 inch Pro is technically thinner as well now, even if the wedge shape of the Air makes the Air seem smaller. They all but weigh the same now too.
> it [The MacBook Air] was honestly never that great to begin with
In absolute terms perhaps not, and definitely not at launch. Later models however offered a pretty compelling mix of price, size and performance for a long time. Especially the performance to battery life ratio, which at various times has been one of the best compromises in Apple's lineup. There's a reason sites like the Wirecutter and the Verge kept it their recommended machine "for most people" for such a long time. I still think later versions of the Air are some of the best machines Apple has made at their respective peaks, again "for most people".
Is it not selling very well? It seems unlikely to me that Apple, as ruthlessly efficient and profitable as they are, would continue making an old product if it's not selling. More likely is that it is selling and selling really well in some segments of the market. I would even conjecture that it is one of the more profitable products in the Mac line-up due to the lower cost of old technology.
The 13" MacBook Pro weighs the same as the MacBook Air (well, the MBP is .06 lbs heavier) and is thinner than the Air at its thickest point (0.59 in. vs. 0.11 to 0.68 in.) . Apple's battery life estimate is longer for the Air than the MBP but that would not be true if they added a Retina display to the Air.
The MacBook Air is better at slicing cake than the 13"in MacBook Pro.
I get that. My point is that Apple's not going to discontinue a product that continues to sell well enough to make it highly profitable. Likewise, if sales are not tapering off then there is little reason to update it unless they can cut costs by doing so.
This isn't the 90s anymore. A computer that's 6 years old is not 16x slower than a brand new one.
I'd say $3000 max.
They basically weigh the same now too (~20 grams between them).