I really wouldn't worry about pre-orders on this iPad.
We here in the niche get excited about iPads and the like, but these will be readily available once released. It's just not a super high demand item, especially the 9.7" Pro that really only justifies itself if the Pro specific features are worth the cost to a person. Most normal tablet people will try out the Air 2 and save a bunch of coin for essentially the same feature set.
The 13" iPP was only constrained as it was a new form factor and the only way to use the Pencil. That model has quickly turned into a fire sale. I can't *believe* all the extreme sales on that of late. Just today a eBay retailer had new, sealed, 128+LTE models for like $880!!
Patience rewards the Apple buyer these days, especially iPad buyers.