Just recently, the case entered a final judgement on April 18, 2018 at the United States District Court in the Central District of California, which declared that the 1976 agreement was not authentic and that "TPC possesses all the rights to develop and expand any audio-visual or other creative works or products based on 'Ultraman' characters or stories". In addition to this ruling, UMC is required to pay damages for its infringement of TPC's rights.
As for what's next, the official press release state that Tsuburaya Productions intends to actively proceed with the further expansion of the Ultraman franchise overseas and thanked the customers, stakeholders, and fans for their support.
[via August Ragone]