The sentence that mentions this is “A handful of ships” and its referring specifically to the Veiled Sea around Kalimdor, which is confirmed to contain Kraken by the Traveler books (point being, very possible the “handful” of ships just got wrecked), and that sentence in itself is a blurb from the Warcraft RPG, which is confirmed to be non-canon. That isn’t to say it’s automatically bad info, because obviously there is stuff in there that IS canon, but not all of it is.
That aside, yeah, it’s totally possible that there is more. The thing is, analyzing maps and globes and seas all means nothing, because Blizzard on multiple occasions has been purposefully vague when asked about this or giving info tangentially related to this (see: The Redshirt question and the language used about pre-Sundering Kalimdor).
The thing is, that can’t be taken as them hinting that there IS an “other side”, because it’s just them covering their butts in case they DO happen to decide to do that in the future. In the same way after WoD’s final raid they kept refusing to confirm if Archimonde was canonically killed in the Twisting Nether or not (because if they did, it would make him canonically perma-dead and they wouldn’t be able to reasonably use him again).
Basically, there’s room for them to do it without contradicting themselves if they really, really want to. But there’s absolutely nothing that confirms its existence currently.
And while that’s the case, I’d prefer they just decide not to do it. Between the map being how it is (if it was intended to be one side, then they would have indicated that somehow, so it’s fairly safe to assume it was intended to be the whole of Azeroth) and the fact that there’s no blatant “holy crap guys we can’t explore the other half of the world because x” lore plot point sitting in the background, it’s pretty clear that they’d have to really shoehorn it into the story to make it work.
They could, but I don’t think it’d be a good way to handle things.
The only thing that bugs me about assuming the map is the whole world and not just one side is the naming of the western and eastern seas. If it were IRL, they’d both just be the Pacific Ocean. But in-game it’s the Veiled Sea and the Forbidding Sea. I think it’s probably just a case of the water around EK being named by Humans and the water around Kalimdor being named by Night Elves (presumably while they were still hyper xenophobic), but it’s still a bit weird.