Yes they have to get some support from somewhere.Not necessarily from BD.Current ARSA have got no support from Bangladesh.Their leadership came from Rohingya community in Pakistan and Saudi Arabia.They trained within Rakhine jungle and then attacked.There are some instance when some Rohingya youth gone back to Rakhine to fight after crossing their family members in Bangladesh.If entire Rohingya people become refugee in Bangladesh then they have nothing to fear about retaliation against their people and can act more freely.Rakhine's mountainous jungle is ideal for guerrilla fighting and a little help from any party they can give sleepless night to burmese security force there.Infiltration is not a problem due to long border and coastline burma have which are mountainous jungle and barely guarded.Even without Rohingya people, there are several million Muslim and Hindu people within Burma who look like Rohingyas.So they can get the camouflage as well.
But the crucial point is, unless burma take back the Rohingya and implement the Annan commission recommendation, this refugee problem will continue decades after decades with bitter relation between Bangladesh and burma and potential to a lot of unforeseen consequences. So, assuming that, once Rohingyas are driven out forcefully, peace and tranquility will reign over Rakhine has no guarranty.It will create another Palestinian refugee like problem.
I would agree mainly but there is a clear difference on what BD will do if Myanmar thinks Rohingya will stay permanently in BD...
BD is currently in the middle of a huge arms buildup and there is no question in some years time that BD will attack and invade at least a portion of Arakan to allow the Rohingya to go back to their homes. Myanmar will just not be allowed to get away with ethnic cleansing and burden BD indefinitely.