I definitely think they should pay income tax, many countries' populations are getting older and there just aren't enough being born to fill their places and support the retired. Having companies which utilize robots pay income taxes could lessen the need for productive immigrants from poorer countries. I doubt such companies would like this but there could be other benefits in other areas that might make robotisation enticing.
They'd effectively be the slaves of the near future. Will they ever have rights if they become sentient? Perhaps, but until then they're something to be exploited. Heck, entire empires were built on the back of slave labour, maybe history will repeat itself in a different hue.
The major problem I see with this is, in third world countries labour is unskilled and unproductive, it would widen the gap between countries which invest in robots, automation and education and those that do not. Robots are preferable to the mass of unskilled and under-educated labourers but they would leave millions without jobs.
Interesting times we live in.
That last bit reminds me of if I will have the will power to become an scientist like I've always wanted. My Dad never graduated high school, my step mom isn't so smart either and her oldest son has a learning disability like her. I sincerely wish to get off these meds in order to recoup my determination.