As playtest material, I would say it is more like getting bombarded with new classes, prestige classes, and/or kits like we did in Dragon magazine in 3e, 2e, 1e, OD&D, so pretty much all the time. At least this time they've very clearly demarked it as experimental.
Overall, I do think that they will either have to do something (or more things) big and bold (I'd say mystic counts, not sure about artificer) and risk stepping on toes or else they will eventually realize that they've made every possible combination of the widgets they've already used.
I have a theory (I think I've touched on it before) that this (no-longer) new plan of one UA a week and getting weekly feedback is them feeling around for where they want to poke their heads out into a new space. We will see, I suppose.