It seems like the logical end for this series.
For the entire 7 book series (2 yet to be published) although a journey for a group of characters, the story seems to be centered on the Iron Throne, with the knowledge that it was a Targaryen who united 6 of the 7 Independent Kingdoms, the 7th through a marriage alliance with Dorne.
Daenerys journey, although she has been in the story from the beginning, the theme was not apparent from the start, which has been to take the throne back (her brother was the one, until he proved unworthy) she feels was stolen from her father, The Mad King. So I’ll be very disappointed if she were not to survive for the final conflict with Cersei Lannister.
And I admit, I’ll be very disappointed if Cersei wins, but honestly who knows with this author? One of several curve ball endings, It could be Gendry who ends up on the Iron Throne with Ayra as his Queen. But it would be a shame if Dragons were not in the final picture, but then you could ask, how would they stay in the picture?
It has been mentioned that the sex of Daenerys’s dragons are unknown, but it is suspect they can change sex, and it’s possible that her 2 dragons could reproduce, if they survive, maybe they are not subject to the same genetic diversity needs that other animals have to produce healthy offspring.
Also, I’m not clear on exactly who can master dragons.
Blood of the dragon is referenced by Daenerys and her brother, the ability of their family to withstand fire, as possibly related to the ability to domesticate dragons, but also related to their Valyrian ancestry, yet they were 1 of 40 dragonlord families. So, my guess is they don’t necessarily have a lock on dragon riding.
https://awoiaf.westeros.org/index.php/House_Targaryen