The Shadowproject has made a major decision, if you own SDC or are interested in the Umbra platform, you should really read this: https://blog.shadowproject.io/2017/03/17/particl-a-new-platform/
Also here is the AMA: https://www.reddit.com/r/Particl/comments/60dpzw/ama_with_the_particl_team_rparticl_march_20th/
TL;DR
You will have to exchange your SDC to particl or sell it within less than a month, or it’s going to be completely worthless!