Gon only had his life & body restored. His nen is still gone since he sacrificed his potential for the temporary power up. It was both a literal loss (his powers) and a metaphorical one (his main character status). It's one of the more intriguing Shonen power ups because Gon's short sighted decision resulted in long term narrative changes that directly affects the reader themselves (since Gon is no longer a featured character in his own manga)
The thing here though, is that as soon as Gon met his dad, he basically reached his goal, accomplished what he wanted, and finished his adventure, that's why the end of the anime is perfect and for his story, even if he didn't lose his nen it wouldn't matter, he accomplished what he wanted -becoming a hunter and finding his dad-, the main story ended here, Gon as a character doesn't have any further need to be present, no loose ends on his part.
So he wasn't going to be featured in the current arc anyway, he doesn't have a reason to go for the dark continent, neither Killua for that matter who didn't lose his power or anything, it's more like a post-content thing where it can focus on other characters -mainly Kurapika and i guess the Phantom Troupe- but there is really no sense of loss since this isn't his adventure