Just to be clear there is a good chance of an upgrade in June as from a business standpoint Apple needs to differentiate the Pros now more than ever from the 2018 iPad.
I would be completely surprised if there are any new iPad Pros at any time this year.
It was 18 months from when the first gen 12.9 Pro was released until the 2nd Gen (along with the 10.5). That was back in June of 2017. These are high end tablets that command high end prices. If they are updated too frequently (and once a year IS too frequent) then that reduces the incentive and appeal to buy them. Paying a premium for a device that will so soon be bettered is not a good thing.
The die-hards in this forum who are looking to upgrade the Pros they bought last year with a new model this year represent an insignificant fraction of the customers at large.
Rumors are swirling around that iOS 12 is going to be a Snow Leopard-like housecleaning release. If that is true, then Apple will most likely hold back on most new hardware features, since that would require additional changes to iOS which essentially defeats the housecleaning goals of iOS 12. They already have their hands full with iPhone enhancements that will require changes to iOS. Porting iPhone hardware features over to the iPad is not as simple and straight-forward as one might think.
For these reasons (as well as others), I'm thinking that the EARLIEST we can expect to see updated Pros is March 2019.
If you were able to justify 2 iPad Pro models in 2 years, then you can easily justify the 3rd in 3. If there is another Pro released this year there will be enough for you to justify to yourself to get that 3rd. If you thought you'd "be missing out on the awesomeness" between the 1st gen and 2nd gen, then your definition of awesomeness is low enough to justify any new Pros that come out this year.

I agree and disagree only because the iPad 2018 is cannibalizing sales like crazy, it’s been sold out of all the BBYs in my district since it’s release and dozens and dozens of people brought in their old iPad Air 2s and more to trade-in to get the new iPad more than those who did when the iPad Pro had the same promotion but were promised even more trade-in value. Reason being is why get a pro when the 2018 has many of the same features and only us Apple fans really know or care about the differences.
BUT Apple would be rather dumb not to upgrade sometime this year. By having a new redesign that is drastic and comes with specs/features customers can just see, without being told, (better and higher brightness, HDR, UHD picture, better cameras, smaller footprint, and almost bezel-less truly futuristic ipads... people will see that and will opt for it.
I have doubts like my first post about seeing a new Pro by June, but still see it as a great possibility as Apple can’t afford to wait another 7+ months to upgrade the iPPs with the 329 almost Pro is out there taking the money and making it so customer service won’t upgrade to pricier iPads.
Plus, just one more jump in processor power will put iPads in MBP 2017 numbers and iMac 2016-2017 comparisons.
and if iOS 12 is stabilized then the iPad will become all that much closer to a laptop replacement (th original 2015 iPP did that *almost* for me p, but the power was just slightly less than a laptop replacement I was looking for. Then the 2017 edition came out and it’s what the 2015 should have been.
The iPad 2018 was like a iPad Pro SE, but with such close features and a design too similar to the iPPs, that people are confused to which is which, and what one is better. Doing a redesign overhaul is the only route realistically Apple can take to keep their iPad sales up. If they wait longer, they run the risk of people who are waiting to upgrade to a pro device to just settle for the 329 one, because it is out now and just has similar looks and really close features.
***apologies if post had any redundancy in it, I didn’t realize how tired I was when writing this***
The two scenarios...
1.) June update to new designed iPad with features that’ll be incredible.
2.) Apple waits for later date (September or Nigember) but when finally updated most excitement is gonewQ.
Kallum.