Besides advanced telecommunications techniques, the most prominent evolution of wireless networks is the densification of network deployment. In particular, the increasing access points/users density and reduced cell size significantly enhance spatial reuse, thereby improving network capacity. Nevertheless, does network ultra-densification and over-deployment always boost the performance of wireless networks? Since the distance from transmitters to receivers is greatly reduced in dense networks, signal is more likely to be propagated from long- to short-range region. Without considering short-range propagation features, conventional understanding of the impact of network densification becomes doubtful. With this regard, it is imperative to reconsider the pros and cons brought by network densification. In this article, we first discuss the short-range propagation features in densely deployed network and verify through experimental results the validity of the proposed short-range propagation model. Considering short-range propagation, we further explore the fundamental impact of network densification on network capacity, aided by which a concrete interpretation of ultra-densification is presented from the network capacity perspective. Meanwhile, as short-range propagation makes interference more complicated and difficult to handle, we discuss possible approaches to further enhance network capacity in ultra-dense wireless networks. Moreover, key challenges are presented to suggest future directions.