well doing a quick analysis, with info off who has posted shows that so far they waves have been every 3 weeks they have been putting out (e.g. October 27th (end of wave 1) to November 10th (end of wave 3) and then wave 4 was November 11th to November 24th? as best i can read).
Also comparing to the consistent and linear growth of pre-orders from:
http://www.vgchartz.com/article/88591/usa-preorders-chart-10-december-2011-old-republic-nears-1-million/
it seems if BW maintains the same rate of wave release, this next wave might be another 3 weeks, maybe bigger because of the fact that the last few weeks before release was a smaller pre-roder base. So the possibility I see is that the next wave might be November 25th - December 10th (if they maintain the steady 3 week schedule they have today).
But this is only speculation, so don't yell at me if they decide not to include the dates i've estimated (after all it is an estimation)