Will Kirchoff's voltage law work in a vacuum
Kirchoff's voltage rule tells us that the sum of voltages around a closed loop in a circuit will equal zero.

Of course, that applies everywhere, even with a lack of conductors. That's a direct result of electrical potential being a potential field.
(this assumes we're in the DC case.)
A potential field is a field, i.e.

an amplitude (here: voltage) defined on a space (e.g. a 2D plane or 3D space), where no matter which path you take, the integral over all amplitudes on the points you travel is always 0 when that path is closed.

The direct consequence is that, yes, even in absence of a current, the voltages add up to zero – just: that has little effect, since there's no charges that these voltages move.
KVL makes a simplification: with a lot of precision, we really only care about the currents that flow through conductors when there are conductors.