How do I migrate from a MBA to new iPad Pro?

Migration assistant will not work. No matter how Apple "sells" the iPad Pro, it is not a computer.there is no way to connect the Mac to the iPad either. As explained, cloud solutions will allow you to move files from the Mac to the iPad and iOS file sharing will work as well.

About File Sharing on iPhone, iPad, and iPod touch - Apple Support

I love my iPad Air 2 and I also have a MacBook Pro. As much as I love my iPad and even though it has become for the most part, my daily go to device, it is NOT a computer and it is still a good bit away from being one. You may want to rethink ditching or giving up on that MBA.

See comments from MichelPM re capabilities of the two devices so keep that in mind regarding apps you may not have access to under iOS.

Migration from Mac to ipad pro?

The other thing is before ditching the MBA make sure that any files (docs) that you have created that have no comparable apps in iOS environment: try to export them into compatible formats that your iOS apps can work with.

I use icloud

download iCloud drive for your MBP (make sure it is upgrade to highest OS)

put all your files/ documents in iCloud drive

go to system preffs>icloud> and turn on options that you want on your iPad

once you get iPad, and sign into iCloud all your photos, contacts , calendars, documents will sync down from iCloud

iOS and OS X are indifferent to one another. Your iCloud storage, Apple ID purchases, email (provided you did not delete if from the server and it's local) will still be accessible, as will syncing the device through iTunes but the majority of anything that is local on the hard drive of your MBA is not going to migrate over, there is no assistant to copy over your local account in this case.

Also, jayleenfromspringboro:

as a follow up to Demo's comments. It is a matter of what your primary uses are.

Like Demo, I am as much on my iPad as I am on my iMac or MBP but they serve different purposes.

Also, since you are getting a new iPad, consider getting a Pencil. If you do a lot of document markup, reviews, editing, etcetera, you’d be surprised how much you can get done on an iPad with a Pencil and some iOS apps such as Notability or Nebo or GoodNotes.

In reference to my linked post, eveything I mentioned, except my early comments about iOS 10, still stand.

iOS 10 became more stable after iOS 10.2 and has had major updates since.

So, no more issues with iOS 10 and looking forward to iOS 11, in the Fall, 2017.

But everything else about iPads VS MacBook/laptops and iOS VS OS X still stand.

Don't give up your MacBook Air for an iPad, but purchase an iPad to use WITH your MacBook Air.

As far as the iPad Pro w/Apple Pencil, try the Apple Pencil out for awhile, in the store, on an iPad Pro before purchase. Currently, I use a much preferred third party smart Bluetooth stylus.

I am NOT a fan of the Apple Pencil, at all, so really try the Pencil out well, first, before plunking down another $100.

Good Luck to You!