Will images come out as PNG files in XWD?

[covoxer]

XX4 exports my JPG images as PNG unless I specify otherwise. Will this be the case with XWD as well?

By default, jpg images are exported as jpg. If you have modified the object that contains jpg, so that it may require transparency (rotated for example), then it will atomatically be exported as png.
But for every object in your design you can set the export type, together with compression level for jpg. Here's the image property used with html export: