In a word, no.
I’m sure some of my fellow PowerShell MVP recipients and other enthusiasts will disagree. Certainly, you can use the Framework from within PowerShell, and that’s a great capability to have. Sitting here today, there are many things which are most easily achieved using the Framework – not "easy," mind you, just "most easily" – such as pinging other computers, resolving DNS names, and so forth.
But as support for PowerShell grows, more and more functionality will be exposed as consistently-named, easy-to-use cmdlets (in fact, both examples I just gave can be achieved using cmdlets from the PowerShell Community Extensions – a perfect example of the evolution I’m talking about). Microsoft’s intent is that .NET is for developers; admins get cmdlets, which map .NET functionality to real-world admin tasks.
WMI is in a similar position. Today, there’s a lot you can ONLY do by using WMI directly. Over time, that will change as WMI becomes a more developer-centric API, and cmdlets become the way administrators work. Those cmdlets may use WMI behind the scenes, but you won’t really care.
So – can you be a PowerShell Super User, today, without the Framework? Well, probably not. But you can accomplish a heck of a lot, especially in PowerShell-ed products like Exchange, SCOM, SCVMM, and more. Over time, you’ll be able to administer AD, IIS, probably DNS and DHCP, and who knows what else, all using PowerShell cmdlets – not the Framework, and eventually not even WMI. So if you’ve heard that PowerShell is based on .NET and that you MUST learn .NET to be effective with PowerShell – well, that’s just not true. So jump in and start learning PowerShell today – it’s just a shell, not a .NET Framework tool.