I have the same issue. I know you can turn bluetooth off in "settings" or turn off the apple wireless keyboard when it's near the iPad and it will disconnect.
However, I'm using this for business and I have the autolock turned on. If I'm using the iPad with the wireless keyboard, and I pack up for the day to go, without turning the settings off or the wireless keyboard off, the next time I pull up the iPad, the autolock screen comes up with no place to type (software keyboard). If I don't have the wireless keyboard handy, there is no other way to turn off the bluetooth, or bring up the software keyboard.
There really should be someway to address this. Perhaps when the autolock shows up expecting the wireless keyboard, you could double tap the screen and the software keyboard would appear and/or ask you if you want to turn off the bluetooth connection for the keyboard.