float minX = Float.MAX_VALUE, minY = Float.MAX_VALUE, maxX = Float.MIN_VALUE, maxY = Float.MIN_VALUE;
for (int i = 0, n = skeleton.skeleton.getSlots().size; i < n; i++) {
	Slot slot = skeleton.getSlots().get(i);
	Attachment attachment = slot.getAttachment();
	if (attachment == null) continue;
	if (!(attachment instanceof RegionAttachment)) continue;
	RegionAttachment imageRegion = (RegionAttachment)attachment;
	imageRegion.updateWorldVertices(slot.getBone());
	float[] vertices = imageRegion.getWorldVertices();
	for (int ii = 0, nn = vertices.length; ii < nn; ii += 5) {
		minX = Math.min(minX, vertices[ii]);
		minY = Math.min(minY, vertices[ii + 1]);
		maxX = Math.max(maxX, vertices[ii]);
		maxY = Math.max(maxY, vertices[ii + 1]);
	}
}

Maybe I'll add a method to Skeleton to do this.

Sorry to drag up an old post, but was this method ever added?

Is it possible to get the current width and height of the current frame at runtime?

see http://esotericsoftware.com/forum/viewtopic.php?f=3&t=1465 afraid I don't know if the method was added.

No, I haven't gotten to it. You'll have to use code similar to the above for now.