Except deleting one attribute set and merge its attributes to the other attribute set. Is there any easy way to merge two attribute sets to just one attribute set for Magento 1.9.2?
Easiest would be to take one of the two sets, add the attributes from the other two it, and then remove the unneeded one.
There is also this if you need to Change Attribute Sets:
While it may not give you the exact solution you're looking for but opens up the possibility of being able to change products attributes sets instead of having to completely recreate products.