Has a post-postmodern artistic sensibility emerged in the 21st century, that may allow for a questioning of the cultural assumptions of postmodernity?
The answer to this question depends greatly on your own point of view and how you read what is happening in culture. I guess the one problem with any post-postmodern philosophy or thought emerging is that, in a sense, postmodernity doesn't really leave anywhere for such thoughts to go in terms of becoming more extreme. Postmodernity at its basis denies any one universal truth and celebrates relativism. As a result, it seems to me that the only way that the cultural pendulum can swing is to move backwards towards the recognition of some universal truths that might impact us all.
You might like to think about this claim through an examination of such concepts as hybridity and diversity in literature and art. The products of novelists such as Zadie Smith, to give one example, definitely are described as postmodern through their treatment of ethnicity and culture and the hybrid mixes that characterise our everyday life. However, at the same time, such examples definitely testify as to a common shared humanity that seems to make the concept of relativism rather problematic.