Scratch that Let's go Eevee and Pikachu aren't the new core games, we are still getting a new CORE series game for 2019, this is just something to hold interest until the second half of 2019. I am glad they aren't just regressing to Kanto fully.
So in summary, the Italian Leaker was full of shit, Pixel Par probably had very little info seeing how he said it was a mainline game and 99% of the 4Chan leaks were fake.