Yeah, it's not for Season 15.
I would say it's more like the first wave of Ninjago: Legacy.
Both are a new subtheme for Ninjago, bringing back the original vibe of the sets. Both have a series of shorts to semi-canonically explain the sets.

Unofficial Conjecture warning
Legacy was also just before a majorly dark season, the conclusion of a three-season arc. I think the reason TLG did that is to avoid having super dark sets, while still keeping the story.

Additionally, some of the larger sets from the Legacy subtheme also appeared in the series proper.
Unofficial Conjecture end

I personally think if I get one set, it will be the dojo. The Ultra Combo Mech is my favourite, but I feel like I have enough bricks to make a larger, cooler version.

Well... it took 14 pages of digging to find this place again 😂... but I had some thoughts regarding season 15.

We know, or at least some of us know, that Overlord, Harumi, Skull Sorcerer, Asphera (I think I misspelled her name XD), Mr. E (YEEEEEEAAAAAAAHHHHH!!!! Favorite Ninjago Villain ;-)), and Pythor are returning. That's quite the lineup... and I think Garmadon is returning as well... though I'm not certain... but anyways, yeah. My question is, where is Nadakan (I probably misspelled his name too XD)?
We know Nadakan is bound to return, I mean, they've hinted at it WAY to many times, and it would make a LOT of sense for him to return this season. We also know the Harumi was toast... or at least, she was supposed to be... and we know that Mr. E was definitely toast, and I'm pretty sure that the Overlord got toasted too. Also, it seems to me that the Skull Sorcerer is kinda powerless without his "little pet skull". Now I know there are a lot of loopholes in what I'm saying here, but could it be a possibility that these may just be Nadakan changing form in order to deceive people? I personally doubt it, but it is something to chew on...

Oh, I forgot I hadn't showed you guys this.
For the first time since Season 9 (Hunted), Tommy Andreasen posted a "two truths and a lie" statement about the next season.

Which do you think is the lie?

Last one is the lie, I'm pretty sure

Whoops! My image was tiny, fixed now. I also think it is the third one, though many people doubt the first.
Let's hope we get a trailer soon!!

I have no doubt in the first, I think it's 100% legit. Part of it is they've seemed to be slacking off in using the Whip, and, especially since they seem to be trying to hold to a lot of Ninjago's roots, I think they may want to try and kinda bring it back a bit more. Giving the song meaning might help with that, and make it seem more part of the show tan it already was. We've seen then do things like this with different apparently pointless characters and elements.

As far as getting a trailer soon... I'm just hoping we get one before the season releases 😂, and not six months after...