Unofficial sources have confirmed that their will be a Rockness announcement this week, possibly as early as Tuesday or Wednesday. In the meantime however two acts that have self announced and one being an almost certainty:
Saint Saviour, aka Becky Jones, is previously know for fronting Groove Armada. She is described as being “an alluring mix of Sinead O’Connor and Kate Bush”, by the Guardian. Interestingly she will be on the Friday night (the same as fellow band mates Groove Armada)
Gary Beck, also confirmed here, as playing on the Saturday night. Proclaimed on his website as “one of the most prolific and inventive producers in the current electronic music scene”.
Finally are Japanese Popstars, no formal announcement yet but have been announced for a "Road to Rockness" event at Sub Club at the end of May. So barring a major up set, an appearance is pretty much certain.
The rest is speculation, but the comedy line-up has not been announced yet and nor has the promised competition for bands to play.