I don't think it's a certainty at all that Tavares would go first. I recall that on TSN Bob McKenzie polled scouts and the majority had Stamkos ahead of Tavares if Tavares was eligible for the 2008 draft, and I think a few had Doughty ahead too. People were noticing warts in Tavares' game by that point. Even at the 2008 WJC, Stamkos was on the top line and Doughty was on the top pairing while Tavares was mainly a power play specialist who played a depth role at even strength.
Stamkos probably goes first, not sure what Los Angeles would do but probably Tavares since they picked Hickey top five the year before and had another first round pick to grab a defenceman in 2008. I guess Atlanta would take Doughty, St. Louis still takes Pietrangelo, and Toronto takes Bogosian.