Google Summer of Code 2019 has been just announced officially by Google. Please refer to this blog for more details about the program next year.
Applications for interested open source project organizations open on January 15, 2019, and student applications open March 25.. The GSoC 19 is planned to run between May 27, 2019 - Aug 26, 2019 Please find the detailed timeline of the program here.
Hope, OpenMRS also will be there as usual .