[simonvdv]

This happened https://github.com/steinbergmedia/vst3sdk ;)

But still, I see no reason to use it over LV2 or even LADSPA.

[p0nce]

There is an obvious reason: implementing a whole new plugin format is harder than just implementing a graphics backend for VST2. LV2 or LADPSA is only useful on Linux IIRC and that's not necessarily a huge audio market.