They are not going to be 'sucked in'. Pressure increase in the cabin (causing inward pressure) happens fairly gradually as the plane descends. Even in an uncontrolled dive, it will take awhile for a plane to go from cruising altitude (30.000 feet or so) to 8.000 feet at which point the outside and inside pressure is about equal.
The only possible rapid change in cabin pressure (that you will hopefully never experience) is a drop in pressure. This will cause the earbuds to be expelled from your ears (assuming the pressure differential is large enough to overcome the friction between the earbuds and your ear canal) because the outside pressure will now be lower than within your ear canal and thus the inside pressure will seek to normalize by expanding.
So you have nothing to worry about.