Honestly, there's really no point in worrying. As I said in the brockley "Global impact of the IPL" thread recently, we simply cannot know what's going to happen.
Ian Botham said earlier today on Eng-NZ commentary something I've been thinking for ages - the IPL would not be possible without international cricket. The whole point is it's established stars - established via their deeds in international cricket. Had it been purely an Indian domestic tournament like the Twenty20 Cup of the Pro20, it'd never have had anything like the TV deals it has.
Yet we could also see a situation where the thing becomes so popular it doesn't even need international stars. We just don't know. It's so completely different to anything that's happened before that there's simply no reliable precedent.
Or on the other hand, the thing could become relatively unpopular after a few years, especially if the golden-goose-effect kicks-in, something that's far from impossible (though also far from guranteed).
We simply don't know. There's no sense worrying. Yes, there is the chance Test cricket as we know it could be destroyed, and it'd be silly to deny it. But if it is, there's nothing as can be done. We've just got to wait and see what happens. It'd be a terrible, terrible shame but sadly, very bad things do happen on this planet from time to time. There's also the chance that the threat will pass - Test cricket has been pretty resilient to date, surviving many possible destructive forces.