IMHO, I agree with dtravis7 - ARM is great for certain things (embedded devices, mobile devices (not laptops), etc.) but it just isn't a desktop class CPU.
I know Apple has a thing about demonstrating the point of view that you can "do more with less", but in reality they need to (for some of the models) put more in for better bang for your buck. Let's face it, a big complaint is still that Macs are too expensive. Some are over priced, some are reasonable, but the ones that are overpriced give the impression that the entire line is over priced.
How many of us that play games have 2 systems? A Mac for daily use then a custom built gaming rig for playing games. Those people are having to invest a lot more money just so they can experience both worlds.
how many people have found that on the Retina display that the refresh rate is a bit lacking even doing menial tasks? (see:
AnandTech - The next-gen MacBook Pro with Retina Display Review a bit down in the page where it shows relatively low framerates scrolling in Safari)
The CPU's Apple is currently using are great, the i5 and i7 are really powerful processors, but the GPU is still second class and lower in all of Apples devices (even the Mac Pro with the extremely aging 5870 that is blown away by significantly cheaper and newer devices).
If Apple wants to improve their Mac sales, IMHO - they need to create more of a draw, better graphics hardware, better graphics drivers - even if they have to surrender that aspect just to the GPU manufacturers (it sucks playing a game in windows and getting significantly better framerate in bootcamp then in OSX) and as much as I love OSX, it needs to draw more people in which means more of a visual update including easier customization (as that's a huge complaint). Better hardware video decoding support would be nice as well; with the advances in GPUs a video editor shouldn't have to suck their entire machine down to do a video transcode when the GPU could reduce the transcode time and allow for the system itself to still perform other background tasks.
Software availability has improved greatly with the arrival of the Mac App Store; although some of their rules are pushing developers away (I understand sandboxing provides better security, but there are apps out there that just won't work well (if at all) with forced sandboxing which is now a requirement for apps submitted to the MAS).
If they want to be a system that everyone (or many more at least) wants, they will need to change their own perspective on what people actually want on their computer for daily use.
JMHO. Moving to ARM would be a huge mistake at this point and if they did, I probably wouldn't be able to buy another Mac due to my other needs and wants because I won't have two systems running at my desk.