Did anyone noticed how Ruby is willingly separating Weiss from Neptune? In the moment they went to investigate the plans of Roman & the White Fang? Where Weiss asked to go with Neptune und Ruby just laughed it off and took her with her?
The two on the bottom left?? They could be, but they could also be a straight couple, or family, or honestly, just friends. That level of intimacy as displayed above is not uncommon at all, especially in Asia.
Knowing the feel of the manga, I highly doubt it would happen like this. If they do get married or something of the sort, it'd probably involve some rather dark and possibly gruesome way of doing so. Not that I'd complain.