Try reading winterbell, its connected to this story and is on going.
Not sure how true it is, but I saw where some said Ygret and Winterbell are both connected to this one.
The order is winterbell, Estio than ygret :)
I don't remember Estio ever being mentioned in Ygret (besides the part where they showed Ygret being found), and I've only read the beginning of Winterbell (I'm letting that one cook). But if Winterbell is before Estio, he wouldn't have been born yet anyways. So they're connected but don't carry on Estio's story. I don't think his story shouldn't have ended there either. I think it could have been wrapped up better with just a few more chapters. But I don't think we have any hope for any extra/special/side chapters unfortunately. (〜￣△￣)〜
It doesn’t directly implicate the connection. There is a family of black dragons who have the power to read others like Estio and some of the dialog are hints. At least if I remember, it’s been a while. I’m sure winterbell is before Estio, but winter bell is not completed yet so not entirely sure.
But ya, Estio could have had a more glamorous ending, but it was better then many other endings of read.
I'M SORRY?? WHAT DO U MEAN "SERIES FINALE"???!! tha.. that's it??? No more of them?? It's done?? For real? NO WAAYYY