I've only recently got my Touchpad and I did a forum search just to check I am not duplicating information but I sent a request today and got this reply:
Thanks for contacting us.
We also want to release the new version of Viber for webOS as soon as possible - just like you! However, since we're also concerned with ensuring quality and improved service, it takes time and we don't have an exact release date as yet. Nevertheless, expect it very soon :-)
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Ticket ID: MAO-140-21485
Department: Advanced Tech Support
This looks good, can't wait!