Yes, I understand that now. I was under the impression that the coin limit was somehow fixed forever and could not be altered (like a transaction deep in the blockchain can't be changed anymore). But that's obviously not the case.
Well, it's kind of the same. The developers could declare that all blocks since block 27000 are invalid, and that miners must start working on a new block 27001. If they did, we'd probably try to find new developers...
Similarly they could declare that they're increasing the number of bitcoins from 21 million to 42 million. Again, hopefully the majority of bitcoin users wouldn't go along with such a scheme.