Not very high whilst we run the power stations :c)
Seriously man's destruction by his own creation is a fear that goes back through stories like Frankenstein (yes I know that Victor isn't actually killed by the monster) and further back.
Terminator is just one in a long line of stories like that.
Seriously though think about all the processes that support a robot. Electricity, mining of fuel for electricity, maintenance, manufacture of spare parts, manufacture of components for spare parts, transport infrastructure etc. etc. That's not even considering the manufacture of weaponry
To take over a world you have to take over the entire infrastructure web otherwise you grind to a halt pretty fast.
That would involve intelligent robots better than any we have running every part of the system.
Oh and they'd probably need to be able to move about too! and that means battery technology way way beyond what we currently have.
I'm not loosing much sleep over it