To add to my earlier post they could show the scene where Ned tells Jon the next time they see each other they'll speak of his mother. The clues are scattered enough that they could open an episode the way I mentioned.
They could do it like they did when Ice got melted down. They showed every scene of the sword then went straight to Tywin having it reforged. So you could flash from Lyannas statue in the crypts to a Dany and Jorah convo about Rheagar to Oberyns mention of Rheagar setting his sister aside to one more possible hint from this season then drop the bomb.
Edit: they could sneak in the snow on the throne from the HotU scene too