It will of course use both, and the mk3 too , already shown in that armaments poster. But jets during deployment are often armed as per mission profile. That means a dual pylon astra mk1/asraam on tejas is as useful as carrying mk3 in another pylon, not engagement wise but armament wise depending on what ever threat it will face during a sortie. Weapons are already standardized up to required spec. Next it comes to the top brass running the op command choice to use the most suitable one.
War situation is such, whatever you plan for & spec it up to your choice, you will always find the need for something else during it. Diversity of weapons is something most air forces crave tbh depending on their doctrine.