Scott Coker lays out the details via AOL Fanhouse:

"We're in dialogue with Gina," Coker said. "We did invite her -- through her manager -- to fight Cyborg on April 11. Cyborg is ready to go, and I think at some point today there will be further dialogue with Gina."

...

"My gut feeling right now is we have a shot at it, and it's 50-50," Coker said. "She'd have to sign, start training camp and get going, but I think there's a 50-50 shot we can make it happen. This first fight card, we're promoting it as the greatest card in the history of Strikeforce. I think we've had some good fights in our history, so we have to deliver."

So much for tune-up fights.  Apparently, Coker is ready to make the match that EliteXC started building toward last year.  My guess is that the odds are less than '50-50' that this fight will take place on April 11.  Carano hasn't even signed with Strikeforce, she would probably like the benefit of a full, well planned training camp before facing her toughest test to date, and she's been in preliminary talks with the UFC as recently as last week according to Kim Couture.  Maybe, this offer is meant merely as a signal to Carano that her signing  is a top priority for Strikeforce.

My unexpert opinion is that Carano will eventually land at Strikeforce, given the exposure the promotion provides through Showtime and CBS.  Besides, they already promote female MMA and have Carano's biggest potential opponent (from a drawing power perspective) locked up.  I just don't  see Carano fighting Cyborg as early as April 11.  Then again, stranger things have happened.