Hey, sorry for revivin such an old topic but I felt that this information would be appropriate to post here.
There is a 'leak' created by (what I was told) was the same user who has correctly predicted Banjo & Kazooie. The same person has had accurate leaks in the past for various announcements, including the reveal of Smash Ultimate in March 2018 as well, so they're surprisingly reliable.
The leak says, among many other interesting things, that Klonoa will be the 5th DLC fighter for Super Smash Bros Ultimate, preceded by Amaterasu from the game Okami.
Here is a screenshot of the leak in question. You can see that the name is cropped out, so please take it with a grain of salt.
I've made some research and it seems that the original 4chan post has been deleted or removed, resulting in a 404 error, but a Google search can bring up that it has existed.
After searching some more I found another post made by user "XalSirhc !!II3mujYxM74" explaining this list once again. Here is a link: https://boards.fireden.net/v/thread/468500381/
The spoilered image reveals to be the fighter's pass, with Amaterasu and Klonoa edited in.
Now I'm not intent on saying that this leak is real, but I will be willing to give it a chance if it predicts a Nintendo Direct correctly for this month. (aka. It has to contain the info mentioned in the 'leak'.) If it happens to be correct we can very well believe that there is some truth to it and that Klonoa has a chance to appear as a DLC fighter.