One hypothesis that I'd put forth is that the crew found out of the three remaining lord's enchanted sleep, at which point they commandeered the ship for themselves.

After this, they could have resorted to piracy, gone back to Galma, or pretty much done whatever they wanted.

It's a simple explanation, and I'm sure that there are some other explanations that would be far more "interesting," but I think that something along these lines is most likely.

I might as well make the joke before anyone else does - the Green Mist ate them!

Fair point, Icarus. Never mind the Galmian sailors, who knew what they were doing, what about the ship? Why didn't it return to Galmia?

Hmm, yes, the Green Mist is probably plausible.

Anyways, my guess is that they were probably just shipwrecked or captured. Chances are in the Narnian world is that they were attacked by a sea serpent or some other great sea beast. Who knows what else is out there? There could be other habitable islands the Dawn Treader crew did not visit. Perhaps there are citizens who are slave traders.

Did Pug's slave traders get hold of them once they arrived in the Lone Islands? According to the book, Lord Berne did well at the Lone Islands, and fought unsuccessfully against the slave trade. Did he really just stop for a pretty face, or did he have a few more things to sort out?

If Pug's slave traders got them, how did the other lords keep going?

The dragon might have ate them, but if it was lord Octesian under enchantment it might not...

I think my favorite explanation is that they abandoned the trip on Ramandu's Island and either went home or died trying.

This is the first time I have bothered to think about it.
The easy answer is that Lewis didn't tell us - it could be one of his "I have not found out yet" replies.
But I think we have to assume that something did happen to the rest of the crew - given the number of dangerous situations the Dawn Treader survived, there were plenty of dangers.

Quite so. So now we are back at what happened to missing Galmian sailors? Drinian had no difficulty explaining how the ship was to return to Narnia, and I'd expect the Galmian sailors might not have any difficulty either.

It was the 7 lords that hired them. Lord Berne stayed on at the Lone Islands, but he never saw any of the others again, or heard anything about them either. Another two were killed en route, then Lord Rhoop went off to the Island of dreams/nightmares, whilst the remaining three were left vegetating at Aslan's table.

Since we aren't told anything different, I'd imagine whoever was left of the Galmian sailors merely took the ship back to Galmia. They weren't deserting, were they?

Since we aren't told anything different, I'd imagine whoever was left of the Galmian sailors merely took the ship back to Galmia. They weren't deserting, were they?

Funny, I hadn't really thought about the ship or the sailors before reading this thread.

But it makes sense that the sailors would find that the remaining Lords weren't going anywhere for a while, and that they wouldn't be required to wait for them to wake up. So yes, then the most sensible thing for them to do would be to go back to the ship and sail it back to Galmia.

Whether they had any adventures on the way, is another question ...

Really, anything could have happened to them. I like the idea that they became pirates, because that would be pretty likely. The trip to Ramadu's Island was pretty dangerous for the Dawn Treader, so the Galmian saliors probably had trouble too since it was so far away. They really could have ended up anywhere.
It is an interesting thought though.