I really hope not! Then again, I don't think Smash WiiU will have serious online issuest launch.

I doubt it.
MK8 and Smash 3DS worked fine at release, I doubt Smash U will have problems.
If it has, then they should dock off points.

Why should the network functionality not being good or stable firsthand?

These assumptions mean that Nintendo didn't include the changes they've made to the 3DS version into the Wii U version. Or didn't lean from it.

No - Smash U is Nintendos über-game. There won't be any online issues for the players which last longer than a few minutes (the time needed to boot up some additional server to take the load).

Brawl's online was non existant.It had little to no options and you had to wait a whole day to find a single match so I'm worried for Smash's 4 online part.I loved brawl despite it's online problems but I hope they manage to deliver this time.

This is Nintendo. Of course their will be issues.

that's a silly excuse for downplaying certain games imho. Unless it's a absolute tragedy....

There won't be any problems except for those few that would experience some lag.