It's no secret that the cast of DC's Legends of Tomorrow would keep on changing from season to season and it has been mentioned on a number of occassions. In a recent interview executive producer Phil Klemmer told IGN, "We're determined to make every part of season 2 feel like its own show. Episode 201 will very much be a new pilot with new good guys, new bad guys, new stakes, new dynamics, new goals."
It's obvious that Rip Hunter (played by Arthur Darvill) will be a constant leader of Team Legends, simply beacuse the show is based on time travel and well, Rip is a Time Master. The only other actor who is confirmed to be a part of Team Legends in Season 2 is Patrick J. Adams of 'Suits', who is rumoured to be playing Booster Gold.
Nothing yet has been confirmed on which of the existing characters we might get to see in Season 2 of Legends of Tomorrow. But it seems like Marc Guggenheim may have accidentally revealed which cast member we'll get to see again in Season 2. In an interview with TVLine Marc Guggenheim revealed,
"Sydney Palmer is a potential 'Arrow' character. But we've actually been talking about introducing Sydney on 'DC's Legends of Tomorrow.' For the record, Ray and Sydney are not twins but they do happen to have an uncanny similarity."
Since Ray and Sydney have "uncanny similarity", Sydney is also likely to be played by Brandon Routh. This means that Brandon Routh will be making at least one appearance in Season 2 as Sydney Palmer which will probably be a one-off thing. But that's not what's interesting about what Marc Guggenheim had to say. Why would Legends of Tomorrow include a storyline with Ray Palmer's brother in it, if Ray's not a part of the Team in Season 2? In Season 1 of Legends of Tomorrow, we have seen Sara's father, every characters' younger self, Jefferson's father and Leonard Snart's father. But did we see Oliver's parents or Barry's parents in any of the episodes? We have only seen characters that are related to the team members. Now, some of you might point that Connor Hawke was not related to any of the team members and that he was Diggle's son. Connor Hawke is an important character in the comics. But Sydney Palmer is not much of an important character in the comics. So, why would the writers include the character if his brother is not a part of Team Legends in Season 2.