Notice how they're doing forms for only gen 1 pokemon. Do you think it's likely they will do more Alolan forms for other gens?
I really hope so, but Game Freak haven't shown any indication that they will yet.
As for the sandcastle, it takes a while for my opinion to form, but I can say one thing for certain: I would have disliked it had it not been for the Ghost type.
I'm fine with inanimate object Pokémon, as long as there is a reason for the objects to have come to life. Muk is a pile of mutated goo. All the Ghost inanimate objects are, well, ghosts possessing things. This one included. It's an obviously supernatural creature camouflaging as a sand castle to lure its prey. Ghosts make things come to life, so it actually doesn't bother me much that it's a sand castle this time. Ghostly enough. Contrast Vanilluxe, which is a living ice cream for no reason. It has no reason to camouflage as a man-made object, no reason for it to have evolved that way, the likeness to an ice cream cone is just... weird and unnecessary.
Also, regarding the "inanimate" part... they are clearly showing this thing move, which is a huge plus. They're showing mobility and flexibility, it's not a dead object hanging still in the air. Another thing that separates it from Vanilluxe and its ilk, which have no moving body parts whatsoever. Grimer and Muk also hinge completely on their movements, without which they would have been the worst Pokémon ever. An immobile puddle with a face?
The last thing that separates it from Vanilluxe & co.: It doesn't have a tacked-on, derpy, smiley face. Its design already gives it natural-looking eyes and a mouth. They don't have to draw flat eyes and a smile on a flat surface.
Vanilluxe is so hated because of a multitude of bad design decisions, which this thing elegantly avoid despite following the same core concept. I think most fans will be happy with it.