But that was anyway on the way down as soon as Bruce returned to be the main Batman again.
I think even as Batman and without the reboot Dick would have been pretty soon down to a single Book, with Bruce taking over all the others.
I think him going back to Nightwing, would have happend eventually with or without the reboot, and if you look at the state of the Nightwing solo and his incarnation of Titans before the reboot. I don't think there was lost mich by wiping them mostly out of history.
The reboot could have actually even been a benefit (if done better) considering how his solo and his generation of Titans got derailed pre flashpoint.
In Tim's case you had still plenty of history from his Robin riun that could have been used (since no one dropped a nuke on it) and his incarnation of Teen Titans was still going storng before the reboot.