Of course, TECO is the explicit ancestor of emacs, as emacs was originally implemented as TECO macros. However, I can't find a paper trail giving similar credit to TECO for vi. That said, istuff<esc> is the same in TECO as it is in vi and TECO (1963) well predated vi (1976). RSTS (along with TECO) was used at Berkeley in 1974 before v6 Unix was installed by Ken Thompson on a sabbatical to his alma mater in 1975. Bill Joy started as a grad student at Berkeley that same year. emacs (1976) wasn't ported to Unix until the 80s.
There's no hard evidence and neither Ken Thompson nor Joy has ever mentioned TECO. So I'm probably wrong.
But I still consider TECO to be the ur editor.