I have a suspicion that there's a good segment of the pre-orders who are prior Scooby owners (like myself)... and who started out with rides like the WRX and STI, but have simply outgrown those cars due to starting families and such.
That said, those same people are used to doing some modifications to their vehicles. Just take a look at some of the comments on here and also at other subaru forums. I can already name at least 3 or 4 parts that would be nice to have aftermarket accessories / mod options.
My guess is that if there is a demand, *someone* will eventually step up to the plate to capitalize on it. Simple market economics.
The only issue is that the car (or rather, parts from the car) has to be physically available for people to look at, take off, and mod.
It will come.... the only question is when.
I would guesstimate that by fall and christmas of this year, we should have at least a few aftermarket goodies to look at and choose from.