I'd be interested in where the idea that people want pre-written content is coming from. That's still somewhat true in the American market - the largest one by several degrees of magnitude, admittedly - but does indeed miss the reality of gaming groups here in Europe. Even in the US, the tendency seems to be going more towards custom content with universal systems.
I only have anecdotal information from the US, of course, but I can point at a few things:
For at least 10 years, my various home gaming groups have been based on pre-written content in not-really-universal systems. Working backwards through time: Pathfinder, Shadowrun 3rd, D&D 3.5, Hackmaster 4th, AD&D 2nd, Shadowrun 4th (very short), D&D 3.0. Then you hit Gear Krieg, whose adventures I believe were written by the GM. It's not far past that where I was in a Feng Shui game with rotating GMs and self-written adventures, but that puts me back into the 90s or very early 2000s.
In the last few years I've GMed both pre-written (in Pathfinder) and self-written (in Paranoia) adventures. The majority of my GMing has been Pathfinder, both in a home game and in Society. The last home campaign I ran was Kingmaker, one of Paizo's Adventure Paths.
Nobody I know runs using a truly universal system. As you can tell from the above I don't really consider D&D 3.x/Pathfinder a universal system at this point, and neither do the other GMs I know. Even if you discount that, nobody I know runs using any system that's more universal about their system, so to speak. (Ex: GURPS, Fate, Savage Worlds.)
Paizo's website isn't working for me right now (I keep getting the "too many accesses" error), but I believe I've read that the monthly Adventure Path has long been their biggest seller and that Pathfinder was created so they'd have a system in print for which to produce AP issues. (My guess is that this'd be in the company retrospective blog posts from not too long ago?)
The practical upshot of all this is that I can easily believe that pre-written content is likely to be the major sales driver even if that's not everyone's experience. Whether that's how it works out is yet to be seen; selling a new content platform is hard. It should be interesting, though!
PS: I hear Realm Works is already decent at helping you create that custom content for your home campaign in a universal system. ;)