It's hard to say but I'd like to say that Starkiller is alive. Considering the Distant Thunder cutscenes I like to think that Vader showed the Dark Clone the "dead" body of Starkiller and then after that Vader awakens or resurrects Starkiller and he has amnesia like Revan did in KotOR. Either that or that there's the Dark Clone and a good clone(the one we control in TFU2) and the original is still alive but in stasis.
Who knows though, the Distant Thunder cutscenes may not even be canon, and may only be used to create some sort of an infinities backstory to the Dark Clone just for the Dark Side ending.
"All too easy."