I recently purchased a new folding bike and after reading many messages on bikeforums about traveling with them, I would never check a bike in a soft sided bag. There have been times when damage to bikes inside hard shell suitcases is reported. There are threads on how to put pvc pipe in your hard-shelled suitcase to keep it from being crushed and your bike damaged. I just don't see it surviving a sewn case. It would be a good idea for transporting on a bus or in your car though.
Claudia
2009 Trek 7.6fx
2013 Jamis Satellite
2014 Terry Burlington