If he can't that essentially renders the main character useless right. Also if he gets his nen back do you think he'll get a different type since he came back from almost being dead. Is there any chance he'll get a different nen nature.
There have been no blatant indications in the manga or anime to show that he will get his Nen back.
In most other shonen manga's you would expect a protagonist who loses their powers to eventually regain them stronger or in a different way. This is best seen in Bleach where Ichigo and his allies does this many times. As Hunter x Hunter frequently is designed to subvert expectations, however, there is no reason to presume Gon will get his powers back.