If Hey! Pikmin was the same project as Pikmin 4, I would like think Miyamoto or someone at Nintendo would've confirmed that by now.
I'm fairly certain the last time we got any news about it was about month prior to Hey Pikmin's release. They didn't give much information about it then, either. All Miyamoto said is that it was "progressing".
This is starting to look like a repeat of the time gap between Pikmin 2 and 3's releases. I wouldn't mind so much, a delayed game is eventually good, after all. I just wish that they'd at least gave us some news about it by this point.