I noticed that both the book on the Dragonborn and the Greybeards say that it is uncertain if there could be more than one Dragonborn at a time. How likely do you think it is that one of the future DLC will add more of these soul-stealing warriors in the game?

Maybe the big DLC at the end will extend the civil war quest and pit the victors you chose against the Thalmor. But you soon discover that the Thalmor have a secret weapon, a Dragonborn just like you, with a mastery of several shouts.

I think it's pretty likely to happen. They may not do it exactly like that, but I suspect a rival Dovahkiin will be brought in eventually.

In my opinion I reckon it would never happen

There probably are other Dragonborns But to find out if you're an dragonborn you need to kill an dragon (or have one die near you) so that you can take it's soul. So far you're the only person (recenlty) who has done this...

even if the thamor had an dragonborn, they would have to kill an dragon first (which they haven't) so no they won't have an dragonborn unless ofcourse they kill an dragon part-way though DLC and discover they are one.

It's entirely possible that there can more than one, if a dragonborn had a son then the son would surely be dragonborn, like the septim emperors. (That's what I think anyway, I don't really read dragonborn lore)

I'm not sure if I'd want a DLC around more dragonborn but if there could be some more dragonborn just wandering about, slaying dragons while my character is busy then that would be great. Like there could be a dragonborn in Falkreath to keep the dragons from killing all my favourite NPC's.

Dun Dun Dunnn

final expansion adds multiplayer so the game doesnt die off thus giving bethesda time to create ES6
also doesnt kill the lore

would be hillarius if this happens

Being Dragonborn is not hereditary, the Septim emperors were not an unbroken line from parent to child and so on. Tiber Septim's direct line ended with his grandson Pelagius; the rest of the Septim rulers were only tangentially related to him and it's unlikely that all or even most of them were descended from a long unbroken line of Dragonborn ancestors. All that is known for sure about being a Dovahkiin is that it is the blessing of Akatosh and is given by him to whomever he chooses, whenever he chooses, and for whatever reasons he deems necessary.

So there's no guarantee that any children of the PC would be Dragonborn. And the prophecy surrounding Alduin's return says that it will coincide with the coming of the last Dragonborn. So... I dunno.

It's also said at the end of the main quest line that Alduin may not really be dead, since the Dragonborn did not absorb his life essence. Alduin may come back, perhaps even aided by another Dragonborn.

The only thing is, I'm not sure why Akatosh would have made another Dragonborn. Maybe he thought that the threat of Alduin may be too great for a single Dragonborn to handle? Of course, this would not necessitate that the second Dragonborn would choose to do as do as Akatosh intended.

I thought it was foretold that the Dragonborn in Skyrim was the last Dragonborn?

I never heard that, but now I think it will be interesting what will happen in some future Tes games

Interesting idea, but it would go against the lore in my opinion. As the other posts have pointed out, you are meant to be the LAST of the Dragonborn.

http://www.uesp.net/wiki/Lore:The_Book_of_the_Dragonborn

When http://www.uesp.net/wiki/Lore:Imperial_Simulacrum takes its place at the eight corners of the world

When the http://www.uesp.net/wiki/Lore:Anumidium walks and http://www.uesp.net/wiki/Lore:The_Warp_in_the_West_(event)

When the http://www.uesp.net/wiki/Lore:Tribunal fail and the http://www.uesp.net/wiki/Lore:Red_Mountain http://www.uesp.net/wiki/Lore:Vvardenfell#Red_Mountain_Eruption

When the http://www.uesp.net/wiki/Lore:Septim_Dynasty http://www.uesp.net/wiki/Lore:Oblivion_Crisis, and the http://www.uesp.net/wiki/Lore:White_Gold_Tower http://www.uesp.net/wiki/Lore:Great_War

When the http://www.uesp.net/wiki/Lore:Throat_of_the_World lies http://www.uesp.net/wiki/Lore:Wars#The_Stormcloak_Rebellion

The http://www.uesp.net/wiki/Lore:Alduin wakes, and the Wheel turns upon the Last Dragonborn.