Trust me it’s going up in price, why...
Imagine if the iPad Pro stayed at 769 base, if the air was 128gb at its base it would be 679 not 579 as it is with 64gb which would be a mere 90 difference in price than the pro if the storage capacities matched.
So if the pro offers better chip (A14X), better speakers, miniLED, Face ID, better cameras, 120hz screen, 5G etc it would be absolutely crazy to even consider going with the Air at the price point with its minuscule storage option.
There is definately an increase in price on the cards for the next gen iPP.
Think it will due to the fact mini led panels will cost more from the sounds