Official Waves OSX 10.10 Yosemite support is planned very soon. We suggest Waves users hold off on updating at this time.
Keep an eye on www.waves.com and the Waves Newsletter for updates.
Exceptions & Notes:
Codex Wavetable Synth:
Codex is a highly complex instrument and as such, can be quite resource intensive. A 64bit system is recommended for running multiple instances.
SoundGrid Studio Application:
For SoundGrid Studio Application system requirements, visit the product page Support tab.