Whether or not the Giants will ever be considered a success is only a matter of time and money.
The more generational support they can build, the more likely they are to succeed, and the AFL have known that from the beginning. From that point it becomes a question of how long can the AFL afford to keep running them at a loss, and something tells me that the AFL will be happy to bankroll them for a very long time considering that they're already making a return from the increase in broadcast and sponsorship value that the 9th game brings.
Sure it's possible that a future administration could look at the Giants, and Suns for that matter, and decide that they could be profitable overnight if they relocated them to more Aussie Rules friendly markets. But the AFL is known for it's long term planning and willingness to bleed money for a better future, so I can't see that happening unless the AFL are forced into it because of extreme financial distress caused by some unforeseeable reason (even then I'm not convinced that the Giants would be the first side they let go).
It's really too soon to even start discussing whether or not they're seriously failing given their circumstances anyway. We'll need to wait at least a generation before it becomes obvious whether or not they're really meeting their targets and connecting with the community, and that doesn't come around for another 9 years (2032).
TL;DR: GWS aren't as much of a financial burden on the AFL as many people like to make out, and they aren't going anywhere anytime soon unless some totally unpredictable, catastrophic, disaster happens that could hypothetically happen to any team in any league. I also reckon that if there's further relocation/rationalisation in the AFL at all, that it's much more likely to be the smaller Melbourne clubs doing the relocating (Norths or St Kilda), not GWS.
You should be following the Super Rugby sides if you want teams in other codes that actually have a realistic chance of folding to death ride. Rumour is that at least two of them are borderline insolvent as we speak, and the rest can't be far away.