To answer your question, no, height expansion won't be featured. Things are pretty much going to be solely focused on "thiccening" type content. Titties getting pillowy, asses getting phatter, MC's dick bulging out some bellies, and such. There are planned to be 2-3 optional choices that'll let you stay size 0 the entire game, or take the expansion events when they pop up and begin the growth. At this point, you could play as Size 1 the rest of the game, or move on to size 2, and so on.
The expansion will be a slow burn style, however, with people getting thiccer over the process of several days or weeks. I want it to be a long drawn-out, but noticeable experience. Slow enough to not be noticeable in the moment, but noticeable in the mid/long term. "I could swear this [insert X article of clothing] fit just fine a couple of weeks ago..."
As for height growth, it's honestly just not my bag. I like size-diff, but I like things to remain grounded in some sense of reality. A giant pair of tits or hips that get stuck in doorways would be considered quite the inconvenience but they can be overcome with relative ease (Ex: turning sideways to fit through doors). Growing 20, 30, 40+ meters tall, just isn't the same. You'd need a house potentially dozens of times larger, insane amounts of food just to survive the day, let alone the week/month/year.
In the fantasy realm, those issues become less so, but I still want them grounded in a sense of feasibility if not reality. A village of 3-4 meter tall giants wouldn't be out of the question, because their accommodations and consumption rates would be large, but not impossible. They could reasonably build houses using lumber from fantasy flora of extraordinary size. Harvesting a giant sea beast could feed the village for days if not weeks and so on.
I guess what I'm saying, is that if you're looking for a Daz3D alternative to "BloomWar", this ain't it (Fantastic little game if that's what you're into). My game's going to be taking a more "realistic" approach to how things work. Factoring in stuff that could be possible if the rules of life weren't necessarily broken, but bent very slightly.
Glad to hear that you're enjoying the game though! I'm pretty close to getting the next update out, so check back soon for some more fun :3