Not much else to say on the topic beside what you read above. Basically for those who use the Facebook app on Windows Phone 7, you can expect an update "...soon" that will finally enable notifications. At least so says Matthijs Hoekstra, Developer Evangelist at Microsoft/Windows Phone 7 development (Netherlands).
Hopefully this will finally bring the popular FB client up to par with other platforms and make it a little more complete.
Update: Hoekstra is now refining his response: "What i meant is that 'an' app is coming for that, not sure about the official facebook app". Take that how you will.