Oh so you know how the entire roster plays and acts then right?
A bajillion times, this.
Seriously, people. Doesn't anyone aside from me remember the speculation that Bowser might be top tier in Brawl after a few people had tried the game at E3? (along with some guy named "Ink" trying to name tripping after himself as "the Ink drop"? lawl)
Bowser will not be top tier because...
1. Heavy characters are almost never top tier.
Top tiers that need to be banned generally evolve from players pushing the amazing speed capabilities of certain characters to the absolute limit (aka MK, Fox and Marth). The odds are that Bowser's "speed limit" will be found fairly easily.
2. Bowser's moveset is AMAZING...unless you compare it to those of the rest of the cast.
Yes, his Brawl toolkit was better than his melee toolkit, but it was still crap compared to most of the cast that just plain had better moves:
-he has no projectile to help him approach or put pressure on opponents, meaning opponents can camp the piss out of him and spam projectiles at him endlessly.
-fire breath tends to do little more than invite punishment in most situations.
-his hitboxes aren't disjointed far enough away from his hurtboxes.
-his recovery was basically the most predictable pile of terribad in the entire game. It was just begging to be meteored or deflected.
One of the big reasons D3 was as high as he was is due to his hammer providing him with great, disjointed range so he could use it while putting himself in less danger than Bowser.
ROB, another Brawl heavyweight, had two projectiles at his disposal.
Also, D3 and Rob both have some amazing recovery.
3. "Big" in SSB just means "Big target".
The best strategy for fighting Bowser is still "Get in his face and pepper him with small attacks so he cannot react." As long as this is the case, he'll always be easy to overwhelm.
Note that the only heavyweights that make it into higher tiers (Snake, ROB, D3) all have not only projectiles but some pretty decent spacing options as well. Bowser has exactly one spacing option: the fortress, which is very easy to punish if the opponent can see it coming.
So no, Bowser is in absolutely no danger of being banned, let alone top tier, let alone 2nd, 3rd, 4th or 5th tier.
If Sakurai reveals a video of Bowser in which Bowser is spitting fireballs across the stage (like he did in Super Mario Bros.), then I might change my tune.