To be able to play online, yes you need to update your system to the latest version,and install the patch for MK8. No, it doesn't matter if you update because we're not going to get anywhere anytime soon.
If you're talking about just using vWii, softmodding via a disc exploit (Smash Stack, any of the lego games) will work on any version, you don't /NEED/ to update but you can. However this has no relevance to the Wii U side of things, it only allows you to install the homebrew channel and run homebrew in the sandboxed (IE underpowered) vWii mode. Think of it as literally a wii inside your wii u, you're using one or the other. (Just know that most homebrew applications have vWii counterparts)