They may (or may not) buff bosses in Naxx (increase their hp and damage) or deliver Ulduar and ICC in a pre-nerf state, that is all, the abilities of the bosses and their tactics will remain the same so there is really no problem, they only would do that because for example Naxx would be the first available tier, and it was just too easy, to the point in retail people with only level 70 gear was able to clear it, and that will be one of the only raids Lordaeron will have for some months, that is why they may buff the bosses to make it more challenging.
Besides it's imposible to be 100% Blizzlike, for example the Crusaders' Coliseum didn't exist until patch 3.1 and was only completed in patch 3.2, yet it will be in Northrend completed from the beginning because we use a 3.3.5 client, TOC will remain closed until release. Not to mention many classes talents and abilities were changed from 3.0 to 3.3.5, and we will only have 3.3.5 talents and abilities.