Boron is great... until you get a fiber in your skin. It is like a barb and can penetrate bone. Real nasty to remove.

I think the next material will be improvements in carbon called graphene. It can be much thinner for the same strength.

Here is the layout of the carbon atoms. Graphene is 200X stronger than steel where as carbon fiber is only 2-3 X if I recall.



Here are some details from wiki:https://en.wikipedia.org/wiki/Graphene