I think you are right that Barbie might be a representation of the hyper-feminine. The fact that it is hyper-feminine suggests it is unattainable. However, it seems that plastic surgery and dieting has become so mainstream that using it to attain a Barbieques figure is fine. Compared to men using work to obtain more masculine (i.e. muscular) builds there is something currently deviant about that behavior. That in itself might be reflective of the changing definition of what is "masculine" and especially the ideal masculine form. In some ways the Barbie ideal will require a masculine ideal to counterbalance it, however, as Ken demonstrated, it looks towards a physiology that is representative of wealth (the toned body) as opposed to one more representative of manual labor (the muscular body).
I am not sure I would agree that the trend is necessarily towards feminizing but rather the erasure of the masculine. Or to put it another way, a trend in broadening the acceptable behavior/endeavors of women by moving into areas/behaviors that have typically been identified as masculine, therefore reducing/eliminating the need of the masculine, and thus not exploring, expanding or even consider the masculine. Or more succinctly, the focus is one women, and to maintain that focus, culture reduces or co-opt the masculine.
That said, there is a counter-trend to reinforce 'traditional' gender roles. This is were I think the Princess trend comes in for women. But I am not sure what is defining men at this point.