Transmogrification of Heirlooms
I'd like to provide an update on this statement I made. It turns out that Heirlooms will be eligible targets for Transmogrification. Also (and this applies to all Transmogrified items), trading, mailing, auctioning or depositing an item in a guild bank will remove the Transmogrified art, returning the item in question to its original artwork. So, while you won't have to stare at the same old Heirlooms the whole time you're leveling, you won't be able to send a set of Heirlooms that have been Transmogrified with tier 13 art to your level 10 alt.
[...] Mainhand can only be applied to mainhand, and offhand can only be applied to offhand. This is partially due to the restrictions on certain types of weapon art.
Again, these are our first tentative steps with Transmogrification, and there's room for modifying the rules later on after the system is introduced, and we see how things shake out. Heck, the rules aren't even quite set in stone right now, and might change further before the system is introduced. (
Blue Tracker /
Official Forums)
Transmogrification as a Gold Sink
The gold cost for Transmogrification hasn't been set in stone, but it's likely to be very similar to Reforging, meaning it'd scale with item level (probably the level of the item actually equipped). (
Blue Tracker /
Official Forums)
Transmogrification Options
The gear also still has to have stats aside from armor on it. That means that there are a lot of white or grey items that might not be available initially when Transmogrification goes live.
As an aside, a lot of people have been asking about hiding shoulders, belts, etc. For now, it's looking pretty unlikely that we'll offer the option to hide anything aside from helm and cloak. (
Blue Tracker /
Official Forums)