Pokémon Black White was announced in April.
Also the only reason SM was announced in February was because of the anniversary. If it wasn't because that it would probably have been announced in May with footage.
This notion that "new gens are announced early" is total BS. X/Y and B2W2 have been...
That a direct is coming is obvious. But the next one won't feature any Splatoon update because... There won't be more. As I said content updates are over, don't expect anything or you will be disappointed.
You are very misinformed.
They confirmed long ago that the last content patch would be in December 2018. Content updates are over.
They also confirmed that splatfest and balance updates will continue until July 2019. After that the game won't be updated anymore...