WSH will be around for a while yet. But Microsoft has definite plans to replace it with PowerShell. So for long-term I'd be more inclined to focus on PowerShell rather than WSH.
That being said, most scripting languages work in similar fashions, so much of what you learn in any one of them can be applied to learning your next.
I think it's more important to start with something (as in anything) rather than wait until you find the perfect scripting language to learn. If WSH looks interesting to you - go with that for the time being. It won't be effort wasted.
Just my 2¢