The problem with including other Shards is that so far all methods of traveling between shards stem back to having the Echo and using it to keep your soul together past your first bodily death and then use it to posses other people's bodies (dead or alive) on the Shard you are traveling too. It's not some nice convent thing you can just do on a whim for the heck of it (like to do random open world content like we do in the current zones). I'm not saying that SE can't come up with different ways to travel between Shards that don't involved essentially commuting suicide. But so far, all travel between Shards has been presented as something that involves going against the natural order of the world and at the moment, that's not something I'd want to be doing. The world is broken enough as it is; I don't want to break it even more. If we do travel between Shards (or back in Time) there had better be one hell of a good explanation as to why we are doing it.

Even we could go to different Shards though, nothing in the new zones we have seen looks like anything we couldn't find on Hydaelyn. Ilsabard is as big as Othard is. And we know even less about what exactly is in Ilsabard then we knew about what was in Othard. The only thing I'd say we know for sure about Ilsabard is that Garlemald is in the far north of it and we've yet to even make it into southern Ilsabard. The entire continent is essentially one giant question mark. And that goes for the New World as well.