It might be a foreshadowing of the rinnegan, but it also might not be. I don't think it can be called evidence that the rinnegan will be awakened. It could also be a panel that indicates that the Juubi sees something that makes it think of the Sage.
The rinnegan is the only physical feature of the Sage of Six Paths that has been revealed, besides his silhouette, and that's why we see the rinnegan. Something having to do with the Sage is happening. Along with the panel before it, maybe the Juubi actually has some of the memories of the tailed beasts or some information was retained from them even after it swallowed them to be reborn.
I wonder if the chakra that they gave to Naruto before they left was supposed to act as a 'scent' or a beacon or something to draw the Juubi's attention. When the Juubi looked at him there's that flame that was drawn around him. It's kinda like, of the thousands of humans that are scattered all over the battlefield, one of them needs to stand out, "Look at this guy!" This chakra, it smells like the Sage of Six Paths. I remember that guy...