Is there any indication that Gon will get his nen back?
No.

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.