What happened to the mana spring?
...haven't decided yet if we'll be transferring the mana springs or not to the new location. Is there enough demand to have a "mana spring" at the new location?
(Nova pointed out that one of the things that make the place quite attractive was the use of SL water. Without SL water it won't be as pretty)
When will people left behind be able to return to the new Lismore?
As soon as they stumble upon the portal that would exist now at the old location, that would let them go to the floating islands.
The idea is that somewhere in the world (where old Lismore used to be, to be precise), there's a portal that allows people to come and go to and from the floating islands.