I think it would be fairly poor design to place speakers on the rear of the device as shown in the picture above so that sound is projected away from the user, unevenly distributed in landscape, and/or covered and muffled by a tablet case.

Anyway, I sent a message to Jolla support in hopes of eliciting a more direct response to a very basic question:

Will the Tablet have speakers?

Answer:

"At this time we have no additional information regarding the speakers/audio. Please stick and stay with us on Jolla.com (and the preceding links) for updates on this and related developments. All available information regarding the tablet can be found on the campaign page."

...

I'm afraid that some of the basics here are not developed enough for a device that is roughly five months from delivery. I'm sure it will be a great device with cool accessories though and look forward to reading about it.