I see a gradual increase in drug co-pays until 2026, however, this article say Tricare fees are held in check for retirees and who are on active duty before 2018.
"Lawmakers also rejected through the legislation a plan to increase Tricare fees for current working-age military retirees or those who will retire from the current force.
A measure passed last year approved higher fees for those who join after Jan. 1, 2018, but gave protection to current retirees and troops through a "grandfathering" clause. The Senate had proposed removing that protection and instead pushing all retirees into the new pay structure, a move that would save $3.6 billion in just the first five years."
https://www.military.com/daily-news/2017/11/08/dramatic-tricare-drug-cost-hike-advances-congress.html