I don't think anyone is seriously saying that Sydney is ready right now for a third side. There are some pretty clear milestones that GWS will need to achieve before it's relevant. That being said, most of the serious discussion of the topic that I've seen in this thread is based around those GWS milestones being achieved (eg sustainable near capacity crowds in the current stadium, or 20-25k crowds consistently in an expanded stadium, comfortable financial position etc). These will likely take 30 or so years to achieve.
Once those are achieved, the hypothetical becomes much more relevant. That being said, I don't see what the harm is in discussing the hypothetical. The thread title after all is "It's only a matter of time". Not "The time is now" or something to that effect.
Then why don't everybody actually talk about a 3rd team not being viable YET instead of getting all defensive over gws and posting up irrelevant population numbers? I mean if it's not now then those population numbers are irrelevant right?