Dante wrote:
The first head of the Dragon was Manetas. That head has been removed.
The second head is Calmemnon.
The third head will be Elandré.
I think it's a mistake to try and connect these new prophecies with the past campaign.
The prophecy in question is below.
I see three heads upon the body of the Dragon
A crown wrestled between them,
They rip and tear
At one another until
The blood of millions
Drowns out the cries
Of their supplicants.
With the next Arc called the War of Paragons. I think you are right about 1 head representing Calmemnon. The other two will be equally powerful beings in the present that fight against Calmemnon. Whether they are friends to us is a different story as the prophecy seems to indicate their battles will cause countless death.