More than the switch to AD&D, people still mostly wrap up their 5E campaigns st the top end of Expert Levels to this day.I believe the usual spoken form outside of forums where the technical jargon proliferates was always -
"You know Basic, Expert, the C One - Companion or Champion or whatever, and then the others,what were they called? we never got that far as we switched to AD&D, wasn't there one where you're like space gods at level 36 or something?"
I pronounces those as "ehn-world" and "Wizards". I've never really pronounced the acronym WotC in my head, just use it as shorthand.
"WAWT-see" for me. To rhyme with "yahtzee"WotC is "what see" to me.