When Vamsi first appeared in the series he was a member of Team Aqua that wants to have his revenge on Blaze. But after Blaze changed the past, he is no longer a villain, and is in fact Blaze's friend.
In episode 97, he talked to Alicea about wanting to kill Blaze. Which Vamsi attempted to do in episode 100, but Blaze's Raichu protected him and fought his team.
Later, in episode 162, Vamsi went after Blaze while he was on his way to Groudon Isle, but failed again to kill him. Instead Blaze successfully killed Vamsi.
In episode 177 Blaze changed history, and changed Vamsi in the progress. Instead of becoming a Team Aqua member who wants Blaze's revenge, he became a friend of Blaze.And therefore is not dead in the current timeline