Dust and humidity can affect any camera if enough gets inside, but sensor-shift stabilization itself is not considered a special weak point. If contamination is severe enough to interfere with the IBIS mechanism, the camera likely has bigger problems already.

In normal use, with reasonable care during lens changes, only small amounts of dust usually get inside, and that typically ends up on the sensor or in places where it has little effect. In fact, many cameras deliberately move or vibrate the sensor for dust removal, and the motion used for stabilization can also help shake loose dust.

Weather sealing matters more than whether the sensor moves. A weather-sealed body, ideally paired with a weather-sealed lens, will better resist dust and humidity. So yes, contamination could theoretically cause issues, but under ordinary use IBIS cameras are not generally more susceptible to sticking or unnoticed failure just because the sensor moves.