Well technically we've already heard that version of the theme tune on a handful of episodes in 1988-89, in fact a couple of those episodes were in stereo too (quite distractingly so too), possibly early experiments?
Must have been. I don't watch these repeats and AFAIK this news wasn't posted on here otherwise I would have checked at the time.
Edit: Actually it was posted about back in April but I guess I forgot all about that. I was more interested in when TOTP went stereo it seems