Actually the ship would have been dumped out of the wormhole on it's own.
No, if I recall the novel correctly, the appearance of the asteroid - a target upon which to fire - was their only hope of escape! It was a lucky coincidence that the asteroid could be used.
Remember Decker's line that I only partially quoted: "Negative control from inertial lag will continue 22.5 seconds before forward velocity slows to sublight speed." It comes right after Kirk tells Sulu to reverse and go to impulse power and Sulu indicates no response. All indicating had the asteroid not been caught up with them in the wormhole the Enterprise would have slowed down on it's own to sublight speed and they would have control again.
He said The Motion Picture, not The Voyage Home.
Hey, I like TMP it's just that it's so.... painful. Drawn out, colorless, and just..., well, masturbatory.
I mean a several minutes long scene showcasing a model. GOD! JUST BOARD THE SHIP ALREADY AND GET ON WITH THE MOVIE!!!!
The presentation of the Enterprise and technology and our reaction to it is a large part of what Sci-Fi is and why I love this movie and why the scene works. And as Wise said he did it was so we get a proper perspective of how large the Enterprise is and then how small it is compared to V'ger.
Yes.
But EIGHT MINUTES?!!!!