Short Answer: No
Long Answer: Noooooooooooooooooooooooooo
Longer Answer: No; large characters almost never end up top tier in any fighting game ever. The tournament isn't high level play for one, people are unfamiliar with the tweaks made to the cast and don't know the ins and outs of this particular version of Smash yet for two, and the game itself isn't released yet in the first place, meaning that there could very well be plenty of buffs and nerfs to come. It's also worth noting that Bowser is still very, very slow; he's faster than Brawl, but his moves still look horribly unsafe. Players will figure out how to punish unsafe moves.
I think a more apt comparison to a character from past games is Ike. Bowser may very well be the Ike of Smash 4: Everyone thinks he's broken during the first month or so of playing the game, then you figure out how to get around his moves and punish his attempts to get in, and he drops to low tier pretty quickly.
