If I buy an iPad Pro from Apple Store, say today and within two weeks we know the 2018 version will come out at the end of the month, can I exchange for the 2018 version?
Yes, they have a no questions asked 30 day return policy
@Apple Stores. This is why so many N-1 products become available on the Apple Refurbished store following new model releases. Also, older models tend to get a price drop when newer ones come out, and some folks have been known to use the 30 day return policy to get the same, older model at the lower price when the new models arrive, or get a model with more storage at near the same price as the original purchase.
Good luck with timing your purchases to fit in the 30 day window. The only products that tend to be fairly regular with regard to release cycles are iPhones which tend to always launch in the same month, give or take a couple of weeks. All others hit the market at various times.
MacRumors does as good of a job of listing anticipated releases on the home page as anyone. They currently state iPad may be getting a refresh this month, but iPad doesn't generally come out with a whole new lineup (standard + Pro) and the same time. Keep your eye on the rumor mill!
For any big releases, there tends to be an Apple Event to 'splain it to the market. For minor spec updates, they can hit with little notice, though rumors will tend to start appearing a week or two in advance when current supplies\shipping dates start to slip, or resellers start dumping current models with discounts to clear inventory for the new models. Resellers tend to know of upcoming releases a week or two before consumers know.