Luigi The President
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TBH that's one of the worst points to use imoEspecially when one remembers the game's director saying things like "If you're expecting trailers all the way up until release, you're sorely mistaken" and "We still have a few more" before Isabelle.
8 characters is not a "few", so either he outright lied (which is a little too tinfoil for me to believe), or yeah, there's probably only like 3 or so left counting Echos at most.
Sakurai's always going to undersell himself. I understand this will cause controversy to say.
5 newcomer trailers is indeed possible. Especially if it's "Everyone is Here! 2.0" with them being introduced as a surprise at the end. The Echoes are nothing hard imo just throw them in like they did with DS and Chrom.
Newcomer trailers can take a minute at most. I think 5 unique newcomers can classify as a "few".