I wrote up an explanation for why I went with Ninninja (for now).
So I thought it'd be good to discuss the naming for next year's series. The shuriken and sentai part are obvious, they're just Japanese words that we all know.
ニンニンジャー Nin-nin-jaa however is written in katakana. It could made up of a few words. Since it's a ninja series, I feel like the middle Ninja should be emphasized, thus nin-ninja or Ninninja as a potential spelling. I know there's a dash at the end, but there've been instances where that dash gets ignored when romanizing a word into English.
Ninninger is the other way it can be romanized. In this case, it's a portmanteau of Nin, ninja, and ranger.
While we're at it, let's talk about the ninnin. Nin by itself can mean 仁 "Virtue", 忍 "To endure (or the first kanji in ninja)", 認 "To acknowledge/Confirm". There is a Ninnin 人々 which means "everybody", but I don't think that makes sense.
On the poster, we see the kanji for nin/shinobi:
忍びなれども忍ばない Shinobi naredo mo shinobanai
"We are shinobi, but we do not hide." since the word shinobi (spy, thief) comes from the verb shinobu (to endure, to hide).
So the puns are rolling already with this one. I can only imagine how many different meanings of Nin we'll go through.
Would you like to join the discussion about it in the thread?
Edit: Made a correction to the slogan which has a better translation. Thanks to Mac and Luna for pointing that out.