Is trading pre-orders safe?

I'm pretty sure preorders can be chargeback-ed, much like any other game bought on Steam. If you used the steam trading system, you might be refunded the items you traded for it, but if you paid with paypal, then you're probably out of luck.

In short, yes, it will be removed. It's as safe to trade with preorders as it is with regular games.

I don't think you can cancel a pre-order once it has been traded. Don't take my word for it though, since I don't have a source. It's just a guess.

Well, thanks for the replies!