>>32892082by this gen's greninja, you mean ash's ace in the anime? I don't think ash's rowlet will evolve to be a decidueye because it's too popular as a rowlet.
stat-wise, it's not this generation's greninja... it's outsped by a lot of mons outside trick room yet outbulked and outsped in trick room
comp-wise, it's still not this generation's greninja. Greninja has a greeat stat distribution and movepool partnered with protean, making it really popular in the previous VGCs. VGC usage stats of the current meta show primarina being the most used in competitions among the starter final stages. Arcanine is the star in VGC right now because of Intimidate and Snarl, so HA Incineroar might be just as popular when released(it can even u-turn to give opportunity to activate Intimidate again). I don't think HA decidueye is gonna be as popular. Unless it gets some battle bond form, which is unlikely given that rowlet is not likely to evolve in the anime.
Popularity wise, I think it's getting competition with Tsareena for a slot in teams as they're both bulky physical attackers, but tsareena has more utility and hp bulk. and also pokephiliacs like female humanoid pokemon. I think it's one of the most molested species in pokemon refresh?