Even 7000km should be acceptable compared to no tank, which is 0 km.This tank won't be ready before 2026.
The South Korean transmission made by SNT Dynamics (EST15K) failed to run more than 7600km. It needs to run 9600km like most German transmissions. It failed South Korean durability tests and the transmission was rejected and went back to development. It will most likely also fail Turkish tests.
SNT Dynamics said they've fixed and improved it and will be ready for 2023-2024 production year. Turkish military is not testing this new version.
Let's say its 2023 and they've finished testing the current transmission, and then another 2 years testing the new SK transmission and then maybe you got something 2025-2026.
Best option is to upgrade Leopard 2A4s until this comes around.
I think using it for now in the first batch and then upgrading it with a newer version or BMC transmission (if it ever comes out) would be a reasonable choice. It is going to be a little more expensive but much better than using old M60s no matter how many times we modernise them.