If we'll figure this out, we'll (very) probably also have figured how out to calculate the effects of communicating with the past. So, no. This doesn't tell us

If we'll figure this out, we'll (very) probably also have figured how out to calculate the effects of communicating with the past. So, no. This doesn't tell us anything about the possibility, it merily tells us, even if it _was_ possible, we're collectively to stupid yet to deal with it without destroying our future which would've led to inventing such a device.