Max von Sydow is definitely in Episode VII. Everything else about his involvement is rumour dressed up as leak. Assuming these claims are to be believed, he is playing a cyborg who dates from the time of the Old Republic and who is an expert on old weapons. Luke's lightsaber (remember that?) is taken to him for identification, sparking off a quest for Luke himself, presumably by Rey and/or Finn. Sydow's character is the friend or boss of Rey (the specifics vary depending on which "leak" you believe). In addition, and most outrageously, he may be an older version of someone seen in the prequels, but not a major character. Many fans are hoping that last part, "not a major character", is wrong and Sydow is portraying a certain bounty hunter who seemingly died on Tatooine... Yes, that's right, the deepest wish of quite a few fans is that he's Boba Fett. According to this meme, Sydow's character is a cyborg because that's all that remains of Fett following his ignominious fall into the Sarlacc in Return of the Jedi. Given the depth of secrecy surrounding Sydow's character, the truth could be equally as strange. And Boba Fett is very popular...