It's a little early to talk about migration path I think. Let's have SPACE be able to do everything NSM can do and then some, and then it makes sense to me to worry about migration. Right now, I wouldn't use SPACE in production - for security that is, it's fine for switching and routing.
I know Juniper were talking about migration plans, but I haven't seen anything concrete as far as tools go, and SKUs and pricing &c. I expect that's still to come.
Not sure how my post generated a migration path argument. I simply meant I have an SRX with an IP on the network and I want to suck it into Space withought scripts or BS. No NSM involved here. Space should just be able to point to the IP and add the device, just curious if anyone has done this.