There's a difference between retooling and rebuilding. They aren't rebuilding. They were happy to get a 26 year old top 6 winger. And I am sure they want to move Tarasenko because he's been a shell of his former self, not because they just need younger. Tarasenko has just sucked of late. They had to lose someone in the expansion draft. I will believe they are "rebuilding" when they move O'Reilly and/or Schenn.
Otherwise, "retooling" just means they are changing things up a bit. Not doing a full rebuild, in which they would just want to get younger across the board.