If you were to take a 1tb HDD and set up the Wii U partition first you should then be able to plug it into a pc and resize the partition to 500gb using disk management from admin tools then reformat the left over 500gb to accept xbox one games.
Not sure if that's even possible though. Think someone would have to try it before you get a definitive yes or no.
Anyway, if you haven't found your answer yet, it's no. Once you format your hard drive for the Wii U, you won't be able to use that hard drive for any other devices without doing a format.