Unfortunately that will never happen, and since packages are the reason anyone uses anything, no one will use the newmacs.
If there were a translation layer for backwards compatibility then that could work, but the one with more packages wins, so I don't think it could work without it.
I have never been limited by it. Granted, it's probably the worst lisp. But it works just fine for it's intended use. It could be argued that is one of the most used lisps.
As for porting packages, some are old and will never get ported and packages are the spice of emacs.
Of course, ES6 is less powerful than Scheme, but the speed and the mindshare outweighed the homoiconicity and the macros :-\
30 years in development do help avoid some pitfalls, though.