i think that teleportation is possible in this Log Horizon universe, right now what i can think of is teleportation between guild banks. since people can access their inventory from any guild bank means it is store in some virtual space which is connected to all guild banks.
so if a world class magic is used players can use this virtual space to travel between guild banks provided there is some form of contact between guild bank owners or owned by the same person.
Now I'm wondering how bank works IRL before the internet era?!