There will be more. Check the main eso website for signups.
Now traditionally, December can be a really terrible time for betas, as even staff in the computer games industry wants time off. Between thanksgiving, the december holidays and New Year's, that leaves, well, very little. Often there isn't time to put together a new build and set up all the stuff for (and schedule for) testing. So it may be a bit before the next beta test. Or possibly not, as other studios have bucked this trend in the past (and currently, as Wildstar is gearing up for a big december playtest)