Any response of substance is likely to be pretty long, and over-generalized, but I’ll try to be brief.
A cross-platform PowerShell will first and foremost provide a consistent interactive experience for somebody working on both Windows and non-Windows platforms. That in itself is a laudable goal. The cognitive switching cost from platform to platform, esp Windows/Linux is pretty high, and one solution was bash everywhere and 20 years ago, it was the only way (MKS anyone?).
Looking forward, though, a text-based configuration is perhaps too small a view of where management is going. With the growth of REST-based services, an API approach to service management seems like a pretty good idea. You could argue that Python takes up that mantle, but I would counter that requiring ad-hoc REST queries to be implemented as a script might not be as quick/easy as you would like, especially if you can just type
invoke-webrequest <serviceendpoint> | format-table ServiceName,Status,Errors.
Lastly, PowerShell is not about supplanting anything; like any tool, you want to use the tool that’s comfortable and can be used for the job at hand. If you have tools written in PERL/Python/WhatEver, use them. But if PS provides you an edge, see how it can be used?
I’m a little biased, of course, but what’s useful to me may be useful for others.