Unkown, none of the Servents of Fate/Extra have had their identities revealed, the only ones who are probably the same are Lancer and Archer, Rider and Caster were confirmed different, Saber probably isn't Arturia and Assassin and Berserker haven't even been shown yet.
Emporer-Wakamoto said: the only ones who are probably the same are Lancer and Archer
I'm pretty certain they're the same, actually. They look to similar not to be (especially Archer).
Saber probably isn't Arturia
Saber is possibly not Arturia. There's not really a lot of evidence either way ATM. She certainly looks similar, but there are enough differences (relative to Archer and Lancer) for there to be an element of doubt.
Also, it's notable that the two servants that have definitely changed are the two whose masters in the Grail War were not the same as their original masters (Caster and Rider). So, it's quite possible that they're changed because the way this war works (apparently, it's a Virtual Reality thing) means that Shinji and Kuzuki can summon servants themselves, and thus there is no excuse for them having Medusa and Medea.
rtdgmdsdff said: Also, it's notable that the two servants that have definitely changed are the two whose masters in the Grail War were not the same as their original masters (Caster and Rider). So, it's quite possible that they're changed because the way this war works (apparently, it's a Virtual Reality thing) means that Shinji and Kuzuki can summon servants themselves, and thus there is no excuse for them having Medusa and Medea.
Bloodletter said: You forgot Lancer, which breaks that theory.
Actually, it can still be true, but it seems a little unlikely for Kuzuki, as never wanted to be involved in the war to begin with. Shinji and Kotomine can go either way.
Well, given the structure of the story, I don't think there's any reason for Sakura to be summoning a servant and then giving her to Shinji. Plus, that would mean that Sakura's backstory would probably need to be sorted out for the purpose of the game.