Most people don’t know the model phone they’re purchasing, or simply don’t care.
IMHO price is what matters to the masses (the XR and and 11 are a testament to that); if this new iPhone (regardless of name) satisfy’ s your requirements and fulfils the vast majority of tasks it’s more expensive siblings do, it’ll sell like hotcakes.
Agreed that a name doesn't make a huge difference either way; I was exaggerating when I said "no one wants to buy and old-numbered phone". They could call it the "iPhone Cheap" and it would still sell if the specs and price were right. HOWEVER, good branding can make a difference on the margins and I cannot see a scenario where Apple would use the "9" name, which would needlessly position it as an old phone.