I want to see Javascript's foundations being totally reworked.
Javascript's performance, large application range and community support gives it A LOT of potential to be the number one language in the globe. It's not quite there yet because it's foundations are weak.
It doesn't provide a reliable platform for developers to trust in. It lacks basic features, It's standard library is poor and it lets too many errors go unnoticed. Once this changes (and it's already changing), there are no limits for what JS can achieve :D
I'm really eager to see this happening.