In the effort to increase data capacity by 1000x, small cell densification is a crucial step and that starts with the existing spectrum. However, getting more spectrum is a critical requirement. In addition to lower bands, operators have to consider bandwidth-rich higher bands with 3.5GHz being the first target. In most regions, this band, as well as many other higher bands are unpaired. So, LTE TDD is a must to access these bands.
LTE TDD small cells in higher bands are one of the most potent solutions to solve the 1000x challenge.