I still miss my BlackBerry, not just for the keyboard; the trackpad was far more precise and comfortable than a touch screen. No awkward reaching for controls at the top of the screen, no fat-fingering the wrong link.
I honestly think their biggest mistake was the BlackBerry-specific data plan requirement, not the slow entry to the touchscreen market.
At the time the data plan was a very useful feature. It worked globally without any additional costs for email. That's much like Google Fi today. I think that it was a major selling point. If BlackBerrys were sold without the plan than eventually it would need to compete with much cheaper devices. I think it is very similar to the model of iPod + iTunes at the time.