IMO BlackCoin could be serious threat to DarkCoin. As a community we should take it seriously:

1. If BC implement DarkSend, DRK could be doomed
2. BC multipool is going to use X11 (this is already happening, it is just a matter of days)
3. I think that more "average Joe" kind of people will consider DarkCoin just a copy of BC because they will firstly hear about blackcoin, which is a big hype nowdays, and they have great  marketing(Apple is big copy-cat, but people find it innovative ).