I absolutely hope this is not the case. Those roles should not become straight-jacket for classes, therefore as a fighter/wizard you won't be shoehorned into being a tank/controller, but that would just be an option. If the roles became straight-jacket during the development process, then the ruleset would be badly rigid IMHO.
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Possibly, but this is quite an advance concept compared to the more traditional classes, so I definitely think it belongs to a PHB2. But the fact is, most of the players that want to play a Gish, they really just want to get the best of both worlds. Fair enough, if the game can support their "needs" then it's better for everyone, but I would put the needs of more general and basic concepts always before.