Are you asking if it can carry the weight of two Dragon's or if it will have the capability to actually carry two Dragon's? For the first one, I don't remember what the expected payload capacity is supposed to be, but for the second one, I'm pretty certain the answer would be "no".
In order to carry two Dragon's stacked, an adapter would be needed stack the two vehicles. This would require a significant amount of extra weight and an avionics system capable of coordinating the separation of the two vehicles. Also, more attachment points would be needed on the Dragon vehicle which are not currently part of the design. In other words, the Dragon vehicle itself would have to be designed to be stackable, and to my knowledge, it is not.
There is also very little reason to do this, as it is not likely that a customer or NASA would need two Dragon's simultaneously and in similar orbits.