I don't think we have to worry too much about more maps in Cantha--there are a few map areas (Kinya Province, Togo's Estate, Raisu Palace/Ruined Kaineng) that look like locks for LW6, and I'm sure we'll get at least one Jade Sea map too.
GW1 Cantha was big, but there was a lot of redundancy. I don't mind if we only get one or two map sections per region as long as they're interesting--especially the Jade Sea now that the color is a bit more, glowy. My long shot hope is for a Maishang Hills + Archipelago + Gyala Hatchery map. That would cover a lot of interesting stuff and, more importantly, have turtles.
I am a little bummed about Old Kaineng though. Why does every old city from GW1 end up as some stony, antiquated pile of ruin? It was only 250 years! Leave it a gross, towering slum the way it was in GW1. Old-old Kaineng had a unique, grungy aesthetic that I think would be cool to revisit. I miss the Xaquang Skyway, running on top of those makeshift skyscrapers was so cool and an interesting map concept for GW2. Undercity would have been a freebie for some sort of instanced content. Maybe we'll get a taste of that if we go to Raisu?
To be fair, New Kaineng does capture a similar sense of GW1's height and expanse--if only there was a little more to do in there. It's a beautiful area and I'd love to see it fleshed out more, maybe with some LS6 related content.
I am admittedly very nostalgic for Cantha.