Yeah, for sure the protagonist will turn into a demon when he ascends to Qi Sea, because right now we’re in a poor world. If we were in a rich one, he would’ve ascended much faster.
In just six months he reached the peak of Houtian — from a coma to a monster. When he reaches Qi Sea, where he’ll have his own internal Qi foundation and won’t depend on external energy, his growth will be insane.
I’m almost sure that in the second book, after reaching Qi Sea, there’ll either be a time skip or he’ll face enemies far stronger — because no one can match a freshly ascended Qi Sea cultivator.
Most likely, though, a war will break out — and during that war, we’ll kill many powerful enemies. The protagonist will mature a lot through those battles. His Golden Seed will probably evolve into a Golden Sprout. That’s when things will start getting really interesting.