...when the S-line gets 19"? Will 19" even be optional on the S4?

Answer's probably yes.

You usually want to put your best foot forward, and get buyers salivating early. Not that AoA ever follows generally accepted marketing practices.

... pricing, options, etc. are still being figured out, much later for the US/Canad market but probably will show up soon on audi.de.

Considering the wheel production delay, it would certainly not surprise me. Then again, forged 18" wheels should be lighter and yield better performance results than heavy 19's, so maybe Audi is going for function over form? All speculation at this point...

... and some have obvious mistakes, like a car with a manual transmission and the driver information system having a gear indicator for a tiptronic.

I wouldn't be surprised if the S4 press photos had the wheels replaced w/ something else.