The line was shot. I've seen a workprint of the film at UCLA, which includes this short scene, and Shatner flubs the take.
(Of course, it's a good thing Sulu wasn't promoted. If he was, he'd probably have departed the series.)
Can you verify this? I mean it sounds interesting and I am not calling you out, but as one anonymous person on the internet to another, this is pretty thin as far as evidence goes.
I only have the audio from the workprint. I may put it online at some point, when I have a moment to edit the roughly 90 minutes (it's missing the last reel, presumably to keep Spock's death a secret) into shorter segments.
This is how I transcribed the scene, which I suppose isn't much help, since I assume it matches the shooting script pretty closely.
Well, Iím delighted. Any chance to go aboard the Enterprise, however briefly. Itís always an excuse for nostalgia.
Well, with Spock as Captain you donít think Iím going to turn anything up, do you?
CUT-AWAY to STOCK from TMP
(looks down at Sulu, looks back up)
By the end of the month, youíll have your own command, the U.S.S. Excelsior.
Well, congratulations, Commander.
Thank you, sir. Iíve been looking forward to that for a long time.
Well I for one am glad to have you at the helm for three weeks. I donít think these kids can steer.