It would all depend on how territorial each of the males are.
If the neutered male was neutered very young - before becoming mature and territorial - it might work.
If the neutered male is an adult and was neutered after he was fully mature, or if he was neutered very recently he may still be territorial and that might result in fighting.
Two intact adult males are not likely to get along - especially if either has previously been housed with a female. If and when you bring a female glider into your home - that might trigger fighting between the two males even before she shares a cage with either.
If you do not have full lineage (a family tree) on your intact male you will never be able to determine if he has common ancestors with any female glider you may get at a later date. This would make pairing him for breeding risky as the joeys might have health issues due to inbreeding.
I would neuter your current male and get him a female companion. They would be most likely to get along well even though he will try to mate with her when she is in heat if he is already mature when you have him neutered.