Originally Posted by pesty

For future reference, the Shimano Compatibility Chart will answer all of these questions. If you already have the SL-R460 on order, you need to get 10-speed derailleurs (105/Ultegra/DA) if you want to keep those shifter, which means you will need an extender or you might be able to make a 10-speed MTB derailleur work. The new 10-speed Tiagra derailleur is not compatible with those shifters.