Can we continue our progression on next expansion?

I spent on Icecrown so many days that I got generally bored. WotLK Raids, WotLK PvP (spells and mechanics), leveling through the old look of Azeroth, etc. Everything is so gray to me.

What I meant by continuation of our progression is enabling characters to travel from older to newer expansion on Warmane. (From TBC to WotLK, from WotLK to Cata, from Cata to MoP.)

Possible problem...
1) What if eventually people get bored on new expansion and want to come back on previous?

I think Warmane can do something like this. Copy and Paste could work? So we will still have our main char. on WotLK with all items, mounts, achievements, friends and in same time we will have exact same character with gear, mounts, achievements etc. on Cata realm.
Warmane, I am aware this may be the cost of server and time...

I can not imagine any more problems, if I am wrong freely correct me and add that problem under question mark, Warmane should know this best.

With enabling expansion traveling, Warmane will get same overall and BALANCED population. Maybe even bigger. Why balanced? People will eventually come to Neltharion with their 80s and continue instantly on 80-85 journey. That way, Icecrown will be relieved. Que will maybe even disappear and new people will come in. Neltharion saved.
Same goes to Medivh people. They could continue their progression on WotLK hardcore realm, Lordareon. People will still spend money on new expansion to stay in top shape, like they do now on Icecrown and Outland.

That would be all from me, could type more, but I want this idea (which I didn't invent, saw it few times before this...) to grow. To be real and improvised. My honest opinion is, that this could be bigger thing than merging Deathwing and Ragnaros back then. This could also bring more people to server and more money.

That would be paid service and, if you wish "a copy" then it would cost "a bit".