All these things are going to happen, just not as soon as we may think. Kishimoto always slows the pace with something, so it's likely we'll hit the 700th chapter before all this stuff happens.
I was randomly searching for pictures of Kaguya on the internet and found some of Hagoromo. I know it's fanfic, but the first picture is really one of the closest we can imagine about the same, knowing that he had a beard and all that. Take a look:
What do you think eh? Looks a little like...
Unfortunately, that's true. Maybe if they summon the Sage back or something, but that's less probable.
This is not a bad idea at all. We can have those "Rikudou eyes" scenes this way. Would be awesome.
I'd like to sincerely congratulate Kishimoto Masashi on this unique performance. This, I believe, is the first time when he introduced a flashback within another flashback. This is fabulous!