hm i dont really know...
In kotor I i liked dantoine and i really loved korriban, korriban was my favourite planet. I like that i-want-to-join-that-academy-feeling. There were a lot of people to interact with.
in Kotor II both planets were recycled. And both of them i likes least. Dxun/Onderon was the best planet imo.
So, if Korriban returns, what could be interesting there? the sith academy is destroyed and noone lives there anymore. For me this is enough, i dont want to visit a planet where hardly noone lives. Even if we can explore other areas, what do you think could be there? ancient tombs of the sith, nothing more. That isnt enough imo.
And Dantoine? well there are more people at least... but i think after beeing in both Kotors the environment isnt that interesting anymore. If they make something real interesting and new out of it, yeah, but i wonder what that could be.
The only used planet I'd like to really visit (apart from Onderon) is a rebuild Taris!
but thats unlikely so we better go with Coruscant!