I sense your premise is false.
Elites who spend ridiculous amount of time and preparation to race or clear content ASAP - they could not care less about others who are not within touching distance of their level. If you didn't even practice PTR, then who are you to them. You may as well be invisible or just a component of the economy. Get nerfed or don't get nerfed - it doesn't matter to them. They often roam servers, sometimes even smaller servers, just for a strong challenge from equivalent players.
Strong groups who can get 4/6 pre-nerf also know that realistically it is entirely possible they could never maintain the rate of progression, extended raids, extra raid days, burning consumes and natural dropouts to clear SWP before WoTLK releases.
Casual and semi-casual existing groups who have cleared all content to date and also want to clear the final content phase of TBC. They know this is literally impossible without nerfs.
New or potential players who enjoy raiding - whether serious or casual - who never got to see any or all of TBC, but willing to put the work in for the final mysterious phase to get geared and into groups with a strong chance to see as much raiding content as possible before WotLK hits. Without access to shared accounts or purchasing geared accounts AND getting into the elite groups, they have again almost zero chance pre-nerf to clear.
Meanwhile, without question, nerfs encourage the players who would realistically never have cleared or even seen some of the hardest original WoW content to keep playing or start raiding and plan their game through into the new expansion accordingly. It is also still not as if HP nerfs will remove mechanics. Regardless, it will still be a serious step up from all previous TBC raiding.