The event 'Vegovision' have already been held in Gothenburg/Göteborg, more info
here.
Djurrättsalliansen/Animal Rights Alliance (founders of Vegomässan) havn't updated the website for a long time.
Pinto (veg. magazine online; in Swedish) updates regularly, so check that site out for info about Vegomässan and other happenings in Sweden/Scandinavia.
There will be a Vegomässa in Malmö Dec 7 10:00-18:00, more info can be found
here. It seems that the information is valid, but havn't checked it with people who is involved with the event.
To be honest, I really hope they found a better location for that event. Way too crowded and maze-like. :/