I do think both will eventually finish what they set out to do.
With Togashi, i am not afraid about him having a writer's block.
I think Togashi has the next two arcs planned out in great detail, it is more a motivational and medical problem with finishing them.
Basically, Togashi makes the Manga more complicated in every arc since Greed Island.
Someone who is sick of what he does or has no fresh ideas wouldn't willingly make it harder for himself and then miss a good ending point like when gon met gin to finish the manga.
The beginning of the dark continent arc was very text heavy, introduced a lot of new characters and dashed in a whole new dimension of politics and intrigue which is definitely harder to write properly than having a tight focus on two main characters like we had when we followed gon and killuah.
Togshi does not deliver a lot of chapters, but I do not doubt his ambition.
I've read enough mangas where the Author lost his ambition or vision at some point (YYH being one of them), but HxH is none of them.
And as long as an author has ambitions, he will likely finish his work unless he dies unexspectedly.