Part of the reason 3RAR is looking to move back to Woodside is because that is where they are originally from. It is their "spiritual home".
As for people discharging due to a move. I doubt that totally. Why on earth would you discharge just cos your reg gets moved. It is an integral part of military life, you get posted where they want you. If they want 3RAR in Sydney, Adelaide or bloody Hobart, you go there.
As for more on why they are doing it. It has to do with the expansion of Adelaide defence. With the move of one of 1st Armoured sabre Squadrons to Cultana (on rotation mind you), DSTO, RAAF Edinburgh, Air Defence Destroyers, Collins class subs etc etc etc, it's all part of a build up towards Adelaide being more of a "defence hub"as it has been refered to.