The new gondola is replacing the very old Merritts chairlift that goes to the 'Cruiser' area. It is not replacing either of the two main lifts at Thredbo, Gunbarrel and Kosciuszko Express. Take a look at the map
here. So even if they let MTB on the Gondola, this would only give you access to the bottom ~3km of the All Mountain trail. There would be no access to the Flow or Cannonball trails from the gondola. The gondola also only gives you 285m of elevation.
Top of the new gondola 1655m (285m of elevation)
Top of the Gunbarrel 1791m (421m of elevation)
Top of Kosciuszko Express 1930m (560m of elevation)
Could the gondola be used my MTB to ride that 3km of the all mountain when the other lifts are closed due to wind? Sure, why not.
But I don't think it's anything to get too excited about. Maybe in 10 years there will be other trails on that side of the resort, but at the moment there aren't even whispers.