talking programming here:

and oop languages mainly.

One feature i can't shake out of my mind as going obsolete is
:
explicit looping
It seems so obvious.

It seems that in say 5 years - 10 years
you wont see codes with for loops using integers.
They'll be extremely rare.
Explicit looping will be reserved just for legacy purposes.

Look at recent codes, it's for-each that's becoming the norm.

2) Null objects.
This was long coming. Null is on its way out.
And modern languages will make it impossible to create or return nulls.
Nulls have their issues and computer science purists just dont like them.
Me,i'm fine with them.