Upgrading normal version to collectors

Q u o t e:
I was wondering if i buy a normal version of cataclysm now to try for server first 85 achievement and then upgrade to the collectors edition later is the normal version able to be linked to another account if i choose to get one.

You will likely be able to upgrade from a standard expansion to a Collectors Edition much like you can from any normal version through the Account Management website.

In those cases though the previous upgrade is not refunded.

I am not entirely certain how this matter will be addressed with Cataclysm though, Lethalloser, we may need to wait until closer to release.