It is the minimum requirement. Obviously your geckos would love more space and I think you'd want to have at least 3 hides. You also want to watch out for fighting. If they are two females they should be fine, but fighting and bullying can still happen!
Two leopard geckos should not be housed in a 10 gallon. The general rule is 10 gallons per a gecko.
When housing leopard geckos together, you should have 6 hides (two of each kind, one for each gecko) to reduce the possibility of fighting and more dominant geckos preventing more submissive geckos from getting into any given hide.
I have slate tiles for my substrate I do plan on getting a 20 gallon tank for my current Leo who is shaping up to be a giant, and I plan on getting another gecko for my 10 gallon tank