The iPhone 6s with Apple's custom built A8X processor is out and apparently the A8X is blowing the socks off of the competition. Now we are waiting for the November release of the iPad Pro with the A9X processors and the word is the A9X will deliver processor and video performance at the very least equal to a MacBook Pro. This gives rise to some interesting points of speculation:

1. I had been considering purchasing a MacBook for my portable computing device until I saw the specs on the iPad Pro and changed my mind. Based on multiple conversations I am not the only one considering that option. It would appear there are a several who are thinking of going from MacBooks, MacBook Airs, and even MacBook Pros to the iPad Pro when they upgrade. Granted there is the issue of iOS vs OS X but with its larger screen, faster processing speed, lighter weight, longer battery life, keyboard, pen, and noticeably lower cost what impact will the iPad Pro have on the MacBook and MacBook Air?
2. Is there a possibility Apple might choose to go with their own custom built processors instead of Intel processors in Macs?
3. Given OS X and iOS are built on the same Darwin kernel and the major difference is OS X's file and local storage management structures
   1. will the two OS streams merge?
   2. is it possible iOS apps could run on OS X?
   3. Will the iDevices and Macs merge into a single seamless product line?
4. How many people would decry any merger of the the two product streams as a sin against God and Mac users?

it's long past due time for Apple to be making their own Macintosh procs. I would be amazed if there's not one pretty far along in their labs right now.

AppleInsider, Computerworld, and Anandtech agree with you and those are all based on the A8X processor. The A9X in the iPad Pro is a major step above that. Motley Fool, a financial not technical house argues the A9X is in direct competition with Intel for the laptop market.

Right now Apple designs but does not build their processors, but if you hear of Apple purchasing or building their own semiconductor front end that will be a sure sign that they have decided to take Intel on mano a mano. It could happen.

I'm surprised they don't already own a fab plant for their iPad process

Apple has never built their own processors. Until the switch to Intel they had always used Motorola CPUs except for a brief period when Motorola could no longer build the PowerPC and they bought PowerPC CPUs from IBM. Apple designs the AnX processors but the build is contracted out. Really not a bad decision as fabs are very expensive to build, the technology changes rapidly necessitating expensive re-builds, and the margin is small. All of that boils down to a small ROI (Return On Investment).

However, should Apple elect to go with their own AnX processors across the board instead of Intel, building their own fab to secure the supply chain might change the ROI computation.