Why does it have to be a conventional supercharger or turbocharger?

Here is an example of a very interesting new technology that combines the best of both worlds, and may be where most of the furture high performance engines are headed: hybrid turbos

http://www.aeristech.co.uk/full-elec...ger-technology

Will there be expensive R&D involved? Most certainly, but it appears that the upper boundary of the N/A engine output has already been reached. Some of the costs might be offset by downsizing to the core Hellcat engine.