cycles vs BI

Lets say cycles engine has finished its development . what would be the point of BI in future since it gves better results

Quicker renders. I model and tweak in BI for quick test renders. Then fine tune it in cycles if im gonna use it.

Not much just speed. Somethings may not need cycles. In Tears of Steel DVD, some shadeless things were rendered in bi for speed. You migh want to do a complex explosion or fire in bi for speed as well. Unless there are settings in cycles that can speed up rendering significantly i see a need for bi for people without the grunt in their computers.

Freestyle, speed.

Exactly. Not everything has to be photorealistic. If you’re going for a stylized or “hand-drawn” look there’s not much Cycles can do for you…

Some people like the control BI gives you over almost all aspects of the scene. You can create some really wild effects that are much more difficult (or impossible) in Cycles due to it’s focus on realistic light interaction and physically based materials. BI is also fast when raytracing is not used, so it’s popular for animations.