If the LABC gets a thruster, even a slow one, they better be buffing up the Seige Cruiser's main gun something fierce or it's going to become pretty useless. Currently the LABC only has an advantage over the LSC in 1v1 combat against other Cruisers. But it is inferior for killing Gunboats, who can solo an LABC with the right loadout and a smart enough pilot. Two LABCs would also be hard pressed to kill a Battleship, while two LSC can do it easily if they hold their distances. A thruster on the LABC could potentially make it so the LABC can solo Battleships and take on multiple Cruisers by itself.
But who knows, it's just a prediction, we'll have to wait and see. After all, some Battlecruisers already have thrusters and they're not rediculously OP.