That depends. Some 'Hairless Rats' are double-rex, meaning they carry two copies of the Rex genes. These are the rats many people will call 'mock hairless' because some of them can grow and lose their fur in phases, while some lose it entirely. If they are bred to a rat carrying no 'rex' they will likely give standard rex rats (curly haired). True hairless is likely recessive and you'll probably end up with a litter of completely normal rats.
Hairless females also make bad mothers.
And there's really no reason to breed just to see the results... The temperment of the rat is what matter, not their looks.