The raids will be cleared irregardless of composition - true. This is because skilled players will always be better than unskilled ones that play a FotM class.
But that doesn’t change the fact that every guild’s top spots were warriors because they did the most damage. I’ve played a hunter for a long time and could barely find a spot since no one wanted more than 2-3. I fear the same will happen with rogues now, because people follow stupid metas.
Don’t fear such things. Class balance in Classic is downright awful, Warriors are so busted it’s hilarious and made worse by all the other specs being so bad. In TBC Warriors got brought down a bit and everyone else gets brought up.
Rogues do suffer in T4 because they are a scaling class and in T4 there is a lack of good Rogue loot, at least compared to other classes (you will still be using a level 68 dungeon blue offhand when you enter T5 unless you get S1 offhand).
But you can’t use the “Rogues suffer in T4” with a Classic Vanilla looking glass, Class balance in TBC is amazing compared to Vanilla, and Rogues are great in T5.