Personally, I think that humanity's view of beauty does not expand or shift much. Contrary to the popular belief of beauty is in the eyes of the beauty, notice how attractive individuals possess flattering qualities that are attractive to many people. This is due to the reason that we find mathematical ratio attractive and appealing as foreseen in the Golden Ratio that is applicable to many attractive stars and models.
On the note of plus-sized models, I believe that society has become more accepting due to the whole acceptance concept nowadays. Social isolation and stereotyping are seen as wrong, and due to the increasing pressure of acceptance, models of all sizes need to feel accepted, and be accepted in society.