A JVM in Java called Espresso is in the works under the Graal umbrella. I believe it has the potential to surpass Hotspot in terms of performance.
This paper: https://www.researchgate.net/publication/319855993_Applying_Optimizations_for_Dynamically-typed_Languages_to_Java says it can eliminate boxing etc.
Given this information, does it really make sense to add value types to the language specification?