Keep in mind that this is just hearsay and a bit of internet sleuthing. I may very well be wrong. But I think a Welsh actor named Wilf Scolding was cast as Rhaegar for Season 7. Last year in late September, Lyanna's actress Aisling Franciosi started following him on twitter. He followed her back, and he also started following the Game of Thrones twitter account and Liam Cunningham. He graduated from a drama school in Wales and it looks like he's done some stuff for the BBC and also a period piece about Henry VIII. He has approximately the right look (very tall, blond, looks a bit like Harry Lloyd) and is the right age. Additionally, he seems like the type of actor Game of Thrones tends to go for: relatively unknown Brit who went to drama school. Obviously, none of us will know for sure until the episode airs, but I'd put money on him as Rhaegar's actor. RIP everyone who wanted an A-List Hollywood actor for this small but important part. Here are some pictures.