Unless more dragons are added, I don't see them falling. Majority of the current dragon areas are very heavily saturated, and with an addition of pkers to the wilderness, these bots could make easy targets (reducing their bone collection rates/hr). It will largely depend on whether or not the new accounts coming in, whether for pking or potential staking will want 70/95 prayer. So many updates can effect this that it's not really worth speculating over. Obviously over time bones will drop, as said, until they either reach a price that is too low and are bought up, or an update causes them to spike.