Just wanted to clear this up since people keep asking me about this. The Black Series 6-Inch General Grievous figure is not a Target Exclusive. He is part of The Black Series "XL" line and will be available at most retailers Spring 2019 with a retail price of $29.99. The Black Series "XL" is not a new Toy Line, just a term they are using for the larger figures. From what I am currently being told, it will have the same packaging look as the other Black Series figures, just in a larger box.
I asked Hasbro for more info on General Grievous and below was the only info they could give at this time.
This figure will not be a Target exclusive. This figure is part of The Black Series line, but will have a bigger box similar to the Gamorrean Guard and Moloch.