It'd be great if a universal sign language became the world's lingua franca. No more accent issues, much less loss of meaning in non-native exchanges. I'm sure some technology will replace language-learning before that has the chance to happen.
Personally I think using English as a linga franca is good enough, as most people already know it, and so there is no reason to do difficult about it.
It's not the first time people try to invent a new universal language, and see it never reach that goal.