Re: Augur - a decentralized prediction market platform

When will this coin list on exchange, is there any plan?

REP is not really a coin. But I guess it's gonna be listed in coinmarkecap in the future as some kind of "asset".

I don't even know if it's gonna work in a (centralized) exchange.

Reason: if you don't use it (report bets) you lose it (to other active users who do).

But sure it could possibly be traded in a decentralized exchange on top of ethereum in the future.

Source: http://www.augur.net/blog/what-is-reputation

I am so upset, I bought many REP but I don't want to do any bet, I just want to sell them in exchange.

REP aren't going to be wagered, i think you didn't read properly. The only way to lose REP is due inactivity, or reporting wrong outcomes on events.
I bout about 8 REP. In the future, you can grow your REP and receive collected fees (based on your % of REP) on the markets that are going to be opened. It is possible to sell REPs when they become a trade-able asset.