Yes, but we don't know what would have happened if Ubisoft continued pushing the online version. It might have flopped or it might have been the greatest Myst game ever with a huge fanbase. All we know is they cancelled it and pushed multi-player content into a single-player game, then in 2006-2007 GameTap picked it up and they even considered a 2nd season when they decided to pull the plug because it was too expensive. Note, however, that Ubisoft might have had more money than GameTap, and could have kept Uru afloat for a while.

They won't be, ever. So the problem will always stand. =)

I once surmised that if the Cleft were really realistic, by now there would be a sort of shanty town grown up around the caldera

That can actually be solved because the problem doesn't come from the fact that we don't have enough people, but it comes from the current system of assignation to default DRC hoods.
Assigning new explorers to automatically created 'DRC' hoods is a problem because it essentially leads to a bunch of empty hoods and many of the few people who are in there are newcomers who, by definition, don't know much yet about the game and who cannot help other newcomers. And we simply need more (and more experienced) people in the default hoods. So that needs to be addressed. One way to solve that would be to assign newcomers to GoG hoods. And make it so that much more new people can be assigned to these hoods than the current DRC hoods number. These numerous people should then be directed to join (or even create) another hood so as to not limit the spots in those GoG hoods with empty 'squatting' accounts. The default hoods should only be a transitory thing for newcomers; much like the entrance of a building: you are welcomed by the receptionist, you ask some questions, you look at a map on the wall, and then you move on.
Although that doesn't solve the fundamental question of the beginning of the game: multiplayer cleft or not?

Most people do not understand Ubi's stance on all this. They did *not* kill it too early.
Uru was not taking in enough subscribers, and looking at the current plans (marketing, community, and development) Ubi did not see a way for things to improve and new people to subscribe in significant numbers. They had hoped that the 'Myst' name alone would allow for Uru to sold millions but it did not, and the only way to enhance that situation would be to throw in a lot of money to dramatically increase both marketing and development efforts. And that was simply too risky of a bet for them. So rather than wait for another year and see no changes (Gametap story) they canned it right away. It was brutal, even seen from the inside, but it was the right decision for them at the time.

(1) The default install behavior of the game is to not create the online account, then passive-aggressively complain to the user about not creating an account even though the default was to not create one.
(2) A flyer distributed with the game indicated that the online game would charge a fee. The game shipped with 5 Ages worth of content that could be experienced offline for no additional charge. So many players (myself included) were in no hurry to sign up for an account and start racking up fees. Ubi did not consider that players might spend weeks playing the offline game before they might sign up for an account.

One way to solve that would be to assign newcomers to GoG hoods. And make it so that much more new people can be assigned to these hoods than the current DRC hoods number.

We have nearly 30,000 accounts, right?
If each of those gave Cyan $10, Cyan would have $300,000. Then we'd probably get everything we need next week...

*Goes and thinks about creating some kind of donatathon event*