While the Fantasy box has HE Sea Guard in it, the 40k box has Dark Angel green marines featured on the front of the box. I'm going to read too much into it but I find it interesting that they'd move away from Ultramarines in favour of the dress-wearing pansies.
However, with DA and Chaos rumoured to be in the 6th ed box due out later this year, it does give stronger credence to those rumours. Although I must say that I'm surprised that it isn't Chaos Marines that they've chosen to put in the box with the alleged push to set them up as the new poster boys.
Make of it what you will. Pinches of salt and all that. Afaik, there'll be less blurry pics out on Saturday.