So, will we be able to easily upgrade/replace those parts in a normal VMWare distro?
I think so. However, the tools they've open sourced are for the Linux/Unix guest OS. They did not open source the Windows versions of the tools.
I'm not sure how easy it will be to take the tools they opened and port them to support Windows guest VMs. I'm sure it's possible, I just don't know how easy or if anyone wants to work on that.
The really interesting potential here is if other VM vendors (XenSource/Citrix, Parallels, and MS) pick up on this and add support to the tools to have them work on various VM platforms. I think there's a reasonable chance of this, except for MS.