They implied there will be no more new stages announced though, which if true would mean there will be no more characters from franchises that aren't already in Smash.
Implying and what actually happens in regards to Smash are two different things they implied back at E3 the would likely be no new characters added and this week we got 5 with a confirmation a few more are on the way so we can't really take what is implied as an absolute.
They never said there wouldn't be any more new characters, they said not to expect many more, and in fact we've only had 2 new ones since if we're taking off Echo Fighters, which they clearly don't count as new characters. It's quite different than them coming out and saying "there are exactly 103 stages in the game", after all they could have just said "over 100" if they were still gonna add more.
But yes, I know. Sakurai implied he wouldn't carry on doing Smash after Melee, Brawl, and 4. You can never be too sure with him.