I expect that you would find very few (if any) transhumanists who would not be at least partially interested in whatever technology was available or affordable, regardless of how or if it aligned with any particular technological theme or clade. Flesh, steel. An enhancement is an improvement.

Why does it seem to you that the majority seems... borg-y?

There's probably multiple reasons for this. Firstly, I would imagine that it's probably a direct reflection of the technologies and approaches deemed most viable or probable today by people alive today. The hopes and dreams of any uncertain future are constructed out of the sometimes unidentifiable shards of the active zeitgeist's glacial decay. Our civilization is driven, fueled - even satiated or pacified - by a vivid ecosystem of steel and silicon technologies. We are surrounded, we surround it in turn - It will remain regardless of effectiveness or appearance. It's difficult to imagine that this tech would not continue to improve - even with diminishing returns. Any material limitations (size/weight constraints, etc) merely serve to ensure that these technologies remain somewhat recognizable in application, conception, and recognition for many years.

How do you fit a novel change into a hypothetical future when you can't describe that novelty in any meaningful or productive way?

Biotech is certainly not stale. I could certainly envision all sorts of incredible technologies built upon biological substrates. The strangeness of a technological approach is never going to be entirely stunting. Details and plausibility aside: Imagine a handheld bag of dust spread across a barren plot by a single man. Within mere days a neighborhood of homes has begun to grow. The density and number of buildings aligns with the population of the nearby refugee camp. It does this without further calculations or assessments. Evolution's blind tinkering already gifted both spore and seed with simple sensors and senses, so why not accept the gift of Nature's Scaffold? There's no shortage of scenarios in which something nature did acceptably is transformed into something potentially world altering. This is a single example. What of biological/medical improvements? Wartime enhancements? Autonomously roaming vessels seeking trash in the oceans across the world.

The unfortunate truth is that the majority (in number or influence) will always have passive control over the narratives and themes presented by the overarching establishment. And when the chrome-dome sparky-bzzt paradigm is what is most familiar, most recognizable, most understood, most fetishized?