RMT = Real Money Transaction, or the trading of virtual items for real life cash.
I spoke with a mod in chat today, and asked about a trade post or auction house. The mod told me that they aren’t really sure which direction they plan to go with it, however one thing which did slip was that each player will have their own online store. When I pressed for details and asked about something similar to an RMAH or items being allowed to be sold for money, there was a change of subject. Further requests for details were promptly ignored.
At this point I can’t say for sure that PoE will be offering a RMAH alternative, only that there will be online stores to allow people to sell their items. So if you have been trading items to others, especially Orange Legendary items, you might want to consider not selling them.
Also I would highly recommend opening up additional accounts, to have as trade mules, or accounts you have for storing rare items as well as Legendary items. However to keep each account safe from the other, in case that the trading of said items does not become sellable via real money, I highly recommend using the HideMyAss VPN service which will allow you to log in each account from a different IP. This will still allow you to sell the items, and not have multiple accounts banned for the service, by using the same IP on them all.