Well I said to drift away because we need a Sun to keep us in gravity otherwise we would pull away, drift. All planets depend on the others especially the sun for keeping in the pull of gravity and keeping our circular, or whatever in the circular motion. If you are saying that a planet all together loses its gravity, then I believe it would become dead in our orbital system. It would be dead unto it's self.
To say that it would implode and such, I don't think so, because it would be dead like a rock. If our own world would cease, our gravity not being there would make all things would die. Our hot inner core would cease and that wouldn't make anything like a Nova, Super Nova or such. I believe we would become like an asteroid type thing that floats around the universe.........