You don't need to wait. As someone living in Stockholm I can tell you that there is not a shadow of a doubt that the riots have a majority of immigrant participants.
The reason is that these riots are highly localized to poor areas where the population is almost exclusively immigrant, being clumped together by Swedish immigration policies. (Map: http://cdn.thinglink.me/api/image/394110718607097857/1024/10...) While international media might have given you an image of a Stockholm of fire, most Stockholmers have not seen a trace of the riots.
With large amounts of youth failing basic school, being unemployed, and lacking parents and role models who have jobs and have integrated into the Swedish society. Riots are almost bound to happen.