Just some inside information from within the SAS Group, there are no plans for the Snowflake brand to disappear, but instead Snowflake branded service is being rolled out across the SAS mainline (and some SK Commuter) flights. The idea is that SAS can offer business class, full-fare economy, and budget class (snowflake) on all flights, and therefore being able to attract the business passengers in business & full-fare economy, and the budget & leisure travellers Snowflake has attracted in the new budget cabin. All-Snowflake flights will remain on routes with strong leisure traffic, like AGP. This is no different than to what Air Canada did to their Tango brand.
Personally, I doubt that we'll be left with just two no-frills airlines. Europe is far too big for just two. I think it'll be left to six.
Most likely, EasyJet & Ryanair, as the big Pan-European major no-frills airlines. Air Berlin/Niki serving the German/Austrian market. Wizz Air or SkyEurope in Eastern Europe. FlyBe as a hybrid no-frills/regional. And then a big no-frills airline owned by a major or group of majors. My guess ... a merger between WW/4U.