Well,we all know how the sharingan has three forms.
Sharingan>Mangekyo Sharingan>Eternal Mangekyo Sharingan.Each form is reached द्वारा doing progessively darker things,but i'll get to that later.

First,the color schemes.The sharingan is Black and red.The byakugan is white.Black and red is usually a color pattern associated with demonic stuff,right?So,in theory,The Sharingan is the Demon Eye.The white of the Byakugan is the complete opposite,as white represents purity,divine quality.Hence the Byakugan,the एंजल Eye.What does this have to do witha possible evolution?Well,i'll explain.

Unlocking the Mangekyo Sharingan requires आप kill your best friend.This,in my eyes,is a step towards the darkness,because आप are severing the ties that connect आप to people.the ties that make आप human.Then,in order to obtain Eternal Mangekyo,you have to take the eyes of another Uchiha and implant them.This is also fairly inhumane,and a bigger step into darkness.In this way,the Sharingan requires embracing your darkness.

The Byakugan,representing the Lighter side,would have a different way to evolve.Instead of embracing your inner darkness,you'd have to defeat it,and remove itfrom your spirit,Making आप basically pure.So instead of stepping into darkness,you'd step into light.You would then achieve a pure version,an evolved form on the एंजल eye in my theory,The byakugan.I know that Sharingan and Byakugan don't really mean एंजल and demon,but they fit my theory.Whaddya think?