In 20 years from now, all of today's children, that were born to a world with cellular technology and internet will be be in their 30's and 40's.
These are the people that will consume technology, use software at home and at office, and will become users of all the new things that are going to be invented till that time.
For this generation, computers are inseparable part of life in the same way as for this generation having 300 channels in the television is normal, and for the older generation having phones and cars.
Assuming that till that time most of the niches will have numerous software packages dedicated to, the thing that will be the differentiator is their level of service, and in the software world, this means the interface with the user is basically its service level.
Having s software that serves its users in a more natural way, that basically reduces the mental burden of the users to a minimum, with a small as possible learning curve, and with maximum efficiency from the user's point of view (minimum work for maximum results) will result in a larger user base, which will eventually translate to a winning software.
You may say that this is the case today, but in 20 years from now, the users will evovle, and would expect nothing less then a perfect usability, in the same way that we are today expect nothing less then a perect service when we buy something somewhere.