I expect it to partially replace and sit above the just-released model:
Early 2020 iPP 12.9:
128GB - A12Z, 6GB RAM, $999
256GB - A12Z, 6GB RAM, $1,099
512GB - A12Z, 6GB RAM, $1,299 <-current model for reference
Late 2020 iPP XDR 12.9:
512GB - A14X, 8GB RAM, $1,399
1TB - A14X, 8GB RAM, $1,599
$100 more than an equivalent early 2020 might seem too little, but remember that with higher storage tier models the margin is already padded by the cents on the dollar cost of storage, plus they will want to entice you to buy this model, so making it a tempting price over the existing ones is key.