Smash Bros games are always announced at E3. So if it does happen it will be announced there with a release date of whenever the paid online is up.
I kinda want Smash 5 more now at this point but if they put a lot of new content that it is like Smash 4.5 than I won't mind. The only reason why my Wii U gets any use lately is because of Smash Bros 4. Once that's on the Switch than my Wii U is going into the closest. (I'm just kidding. I still use it to play Virtual Console and Wii games.)