IIRC, the Völuspá has only one mention of the dwarves. The reference has them standing before "the doors of stone" right after mention of a council of the gods, so possibly a door guard? Or possibly out of the battle guarding their own?
Since Ragnarok is the battle at the end of the world and the world still exists Ragnarok can't have taken place yet. :-)
Also, it's fiction so as far as I'm concerned your view on the presence or absence of the dwarves at Ragnarok is as good as anyone else's.
YMMV!