We've been told by two people that the goal at Sigma is to have the new Sigma 50mm f/1.4 Art series lens to retailers around mid to late April of 2014. No official release date has been given to any of Sigma's distributors as of yet.
Official pricing is expected in late March/early April along with a followup announcement with specifications, sample images and some additional marketing.
At this time the April goal is just that, a goal. There's always a risk that ample production won't be ready by then.
One piece of good news is that the Canon mount version of this lens will be the first to be released (along with the Sigma mount I imagine).