I've been in the business for 30+ years, and collecting/creating sounds for much of it. My general goal has been to find interesting, unique, usable sounds by being in the right place at the right time (through planning or prepared luck), or to create, through regular guided randomness exercises.
I plan to drop smaller libraries that follow some sort of theme, but they may span across many seemingly unrelated categories. Metadata will be UCS compliant, with enough detail (hopefully) to bring them up in a variety of useful situations.