Would you say that, with given effort and hard work, anyone can create a "Smaug" and these beautiful reference sculptures or is it reserved only to the truly gifted?
Oh, and happy holidays!
I do think there is a certain amount of general "base talent" needed, but that's mostly the creativity part I guess.
If you feel comfortable sculpting - doesn't matter if in clay or digital - then all you have to do is to keep practicing your craft.
With dedication and patience I believe that you will eventually excel at what you're doing. But no matter what kind of artist you ask, be it a digital or traditional sculptor, a painter or illustrator - you will be spending the rest of your life perfecting your craft and the way you go about it.
If you never stop learning there really isn't anything that can hold you back from sculpting a Smaug of your own :)