honestly, something like anbu itachi will probably never, if rarely ever, happen again. some time before that we had ninjas like gnw sakura (multiple times), gnw choji, hebihime, gnw sai. for a period of time, we also had sasuke + skillbooks, naruto + skillbooks, etc.

sign in ninjas will generally be very niche ninjas (ofc, nearly everything is good for new players lol cos they dont have a lot of choices), but never something meta. itachi anbu was a once-off occurrence and you shouldnt really get your hopes up.

add to this: cn often gives ninja fragments and their skillbooks for sign in rewards if the breakthroughs were recently released. they've also given kinkaku/ginkaku/naruto ramen frags and skillbooks

we've had this a couple of times with team 7, but until oasis decides to seriously implement skillbooks/trials, we'll probably not get such rewards