Lidstrom wasn't generational. Generational are players who are clearly the best player from their generation or have a very strong claim for it. It isn't position based. Lidstrom was never voted the best player in the league by either the writers who cover the game (didn't even finish top 3 ever) or by his peers.
The only clearly Generational players since expansion are Orr, Gretzky and Lemieux. Past that, you can make very strong arguments for Crosby, Ovi and Hasek, and Jagr to a lesser extent. McDavid is making a very strong claim. Past that, I don't really see anyone seriously in the discussion. So, I doubt Dahlin ever gets in it. Great young player, but I don't think he'll ever win multiple Harts or Lindsay's, which is what generational players do.