This is a concern of mine too. I wish they would stop removing instances. Level 80 onyxia raid could just as easily been accessed through a side door, thus leaving levle 60 onyxia intact. TOC 10/25 and TOC 5 man use different extrances for different instances.Besides, what will happen with the current 10 man lvl 70 Zul'Aman? Its going to be removed or what? I wish Blizzard could just release another part of Zul'Aman...
This would level level 70 Zul Aman as it is, but still allow the levle 85 5 man version to co-exist.
Uh they told us they would be doing this before cata launched.
Each new teir will have 5 mans that provide gear roughly equal to the previous tier, to allow you to gear up alts faster and to allow you to start on the new tier without having to farm old content for months on end like we used to do in TBC.
Raid kara/gruul/mags to do (heroics to do) SSC and TK, raid SSC and TK to do Hyjal and BT.
And that was the only way to progress. We didnt even get badges of justice until later on in TBC.