Frankly . any further delay we get to experience now on would be attributed to GOI own policy of min 50-60% indigenisation / 50% Indian value addition / Import substitution / phased indigenisation related. HAL had been very happy to import anything & everything so far, but they have been told by the MoD over the past 12 months to stop importing & make locally/do the above steps etc. ADA and the indi LRU lists have lots of import substitution pending.
Even right now , say CVRDE or other lab, if they have to make an import substitution related to Tejas, for that you need to test and make the particular item and you obviously would need to import some test material, sensor, fastener or anything related that are not available within the country. So they have to write to MoD first & get a clearance, mere getting that clearance now takes 6-7 months whether it is DRDO lab or BEL/HAL whoever is doing the work. You can get idea of preplanning needed to keep in touch with schedule. Impossible to do so and maintain 3-4 year strict timeline. Local import substitution also needs time to get certified for airworthyness.
In essence, there will be significant delay, and it will be fully due to Govt own policy, which the Govt is very happy with.