Not all Sukhois we have are of MKi standard. The first batch were eight Su-30MKs, the basic version of Su-30. The second batch were 10 Su-30MKIs with French and Israeli avionics. The third batch were to be 10 Su-30MKIs featuring
canard foreplanes. The fourth batch of 12 Su-30MKIs and final batch of 10 Su-30MKIs were to have the AL-31FP turbofans.
Thereafter, license production began at HAL, with first aircraft delivered in 2004.
So, it might be the case, that older su-30s are not upgraded by MLU standard. These older aircrafts might be retired after 2035. This opens a space for about 50 ORCA for IAF.