if you want them now, use the beta:
Release Notes for build 773
The enhancements and modifications below are in build 772 of TWS. To identify the build number, on the TWS Help menu select About Trader Workstation. For clarification on any of the items listed, refer to the appropriate section in the User's Guide, or contact IB customer service.
Enhancements
Trailing stop orders enabled
TWS now allows you to use trailing stop orders via Smart order routing. To create a trailing stop, click in the bid (sell order) or ask (buy order) field of a market data line to create an order, and in the Type field on the order management line select TRAIL as the order type. Use the Aux. Price field to set the trailing amount (defaults to $1.00). Or use the the Order Ticket window.
For more information on trailing stops, see the TWS User's Guide.