Impossible meaning "we aren't sure how to build this today" and impossible meaning "this grossly violates our understanding of the basic physical laws of the universe" are two different sorts of impossible.
And with a better understanding of the basic physical laws of the universe, things that were once thought impossible may become possible. One day, perhaps, even the speed-of-light constraint will need to be revised in light of newfound physical knowledge.
An obvious analog of the correspondence principle [1], usually stated in terms of QM and Newtonian physics, holds here. It's going to take more than "new physics" to change the behavior of sound in this rather-well-understood regime, it's going to take physics-breaking-physics.
There's a time and a place for "we may learn new things in the future". This is not that time. There's no room for "new physics" to be hiding here, short of postulating outright magic, which will probably have a great deal more applications in the world than salvaging something that was always frankly a silly idea anyhow.
I mean, why go to bat for this idea anyhow? It's not flying cars or FTL, it's an incredibly annoying, inferior way of doing something you probably do every day already, and you aren't sitting there going "Gosh, this is a really inconvenient way of charging my phone and there's nothing I can do about it", because there already is something you can do about it if you just can't stand wires. Inductive chargers work and are years-old off-the-shelf tech. I have a cousin-in-law that was involved in marketing them. (It doesn't "beam" the power, but, well, that's why it works. EM beaming certainly seems to be "less" impossible, but probably never practical for ambient personal electronic charging.) Even if this all worked as claimed it would still be yawn-worthy tech. Hardly a reason to resort to nuke-the-entire-philosophical-world arguments about our complete ignorance of everything everywhere ever.
Maybe, but your point is nothing more than heresay.
The speed of light constraint also has nothing to do with light, it is the speed of information travel.
What is being proposed by ubeam is like lifting a 50 ton rocket with 10 tons of thrust. It doesn't really matter what future physics we have, fundamentally its impossible as stated. Bringing future physics into the mix is moving goalposts in an attempt to appear open minded. The rockets never going to lift off with 1/5 of its mass in thrust.