Yeah, as he grows, it should be expected that he evolves into something greater than a plague dragon but I suspect that it will be quite the amount of time before we get to see it happen. It's only chapter 19 after all.
This is OK but I really wish there was more story about him interacting and trying to join human society. The fights are cool but they're super drawn out and boring with a bunch of internal monologue about how he should fight. But it's still good enough to read, I just hope that they continue to focus more on him helping the humans.