The GM's in TW have never showed off much, it has been like that from the beginning. You have no way of knowing if they are active or not if you can't see them and don't know where they are. Nonetheless, GM's showing up or not still has nothing to do with which version would shut down first.
Whether or not a version has more natives than others, that doesn't mean it has more players in general. Not like it matters, though. TW has a fairly big amount of players compared to KR (and way more foreigners than HK, as everybody knows), which alot of them still cash.
HK would probably shut down first, as it was never as popular/successful as TW, outside its native community. Plus, even if TW were to end first, I doubt many people would move to HK. Not only because of just having to start over, but because of starting over and knowing that HK awaits the same fate.
Now, what could be deciding the end would be the removal of GameGuard. My theory:
As a possibility, they've given up on the game and are just keeping the servers up and running to milk as much money as possible. They don't care what happens, so they don't need to pay for GameGuard anymore, thus saving up more money.
Where is this money going? Certaintly not to new updates, as far as we've seen. It is most likely being saved up to fund for the company's other games, or perhaps a new game they plan on adding.
With no KR version to get the updates first and test them out, they'd have to release them in TW/HK now first, but will they do that? I don't see any sign of that happening, since it's been so long since the last (real) update.
When things start dying out faster, we'll probably get that new pet update to keep meta players hanging on for just a little while more, and then finally reaching the same fate as the KR version.
Now, we don't know if the end of the KR version really means the end of DBO. If they have one less version to worry about, maybe the others will profit from that and things will start looking up. Or maybe they plan on an English release (unlikely), which would raise the popularity even more than it ever was, starting a completely new cycle of new players and a bigger, fresh money flow.
Either way, can't deny that things look bad, but there's nothing else to do but wait and see what happens, while still doing what we can, by e-mailing them and showing our concern and keep playing. Especially since there's really no garantee yet that the game itself is doomed completely.