In OTL the Greco Bactrian Kingdom conquered parts of India [183-180 BC] just before a revolt in Bactria split the kingdom into two parts [179 BC], with the old dynasty ruling the Indo-Greek state and the usurpers ruling the Greco-Bactrian state.
So, my question is: What would happen if the usurpation doesn't happen? Would the Greeks rise to dominate Central Asia, Persia, and [at least most of] India? Could the division still happen, but by design like the division of the Roman Empire? What would be the impact on the relation between East [including China] and the West?