To be honest, for 60fps, and now with VR - 120fps and more - it won't be good enough. But... I could be wrong... Lots of games do have additional scripting languages (.gsc in COD games, lua in others, etc., etc.) - these all have garbage collectors. The key to control that is checking your high watermarks (while playing the level), and doing incremental GC.

Whether you can write the whole game in it - I don't know, but it'll be pretty good for tools/editors/pipeline/etc.