Depends on the individual. I'm much faster on a good software keyboard with auto-correct and tap-to-complete. There's a ton of room for improvement and innovation in soft keyboards too. I'm not sure replicating a physical keyboard on-screen is even the optimal approach. In 5 years we might have soft keyboards that barely resemble a QWERTY keyboard. Especially on tablet devices with more screen space to play with. I think the next incremental step is probably grammar / style correction based on analyzing your writing style. For power users who need to do heavy duty text input on mobiles you could have a short hand style input system that allows you to input text at brain speed to be revised before sending into a proper language. You might switch between all these different software input types for different tasks. I don't think physical keyboards will disappear anytime soon but they may increasingly become a security blanket in the form of a Bluetooth keyboard you keep in your back pack just in case.