I very much doubt Apple has any interest in designing their own laptop chips when Intel is clearly doing just fine in that area for them. I can imagine having to support 2 different chip technologies in OSX is a burden, based on the interim when they went from PowerPC to Intel around 2006. And based on what it sounds like Intel's main focus is currently, I'd say they've already got plenty of ultra low power mobile computing chips in the pipeline.
Apple has a history of changing chipsets. Before the Intel transition it was 68k to PPC. You can make a case that switching chipsets every ten years is part of their business strategy. I don't know if I'd go that far but certainly it wouldn't be a huge or unprecedented move for Apple.
They switched to Intel because PPC fell behind in the laptop market where they were starting to sell a greater percentage of computers. A lot of things have changed. Apple now sells more iOS devices than computers and they have a wealth of system building experience because of it. The technology from the iDevices is root of all the major "innovations" in Apples laptops.
Apples ARM chips have a higher performance-per-watt than anything out there including Intel so, no, I don't think Intel is doing "just fine" in the area. Apple sells computers at a high premium because they are different. If anything the last 8 years have been a hardship because Apple's hardware is basically an over priced commodity item. Apple had to do that in 2006 because they didn't have the means of competing against Intel based systems. They do now.
In 2006 there were many great PPC proc in the timeline. All the major game consoles used them if you'll remember and Freescale was working on a dual core G4 that smoked a mobile Core processor but the long term stability wasn't there. Apple couldn't throw enough weight around with its chip designing partners. Well now Apple is a top chip designer and Intel is playing catchup. Yes, Intel's desktop and performance laptop chips are better but the G5 was also better compared to the Xeons back in 2006. Apple still switched.
Now, I have no special knowledge. I could be wrong. But there is strong evidence that 2014/2015 could be the year Apple announces another chipset migration. Regardless at some point it WILL happen because Apple already developed for both the ARM and x86. Bringing everything over to ARM would mean UI tweaks (I don't think we'll see Win 8 style convergence any time soon) but fewer code bases and optimizations to maintain.