If necessary they could pull 3 off the USAF line and deliver them tomorrow - and throw some money at the maintenance budget to shorten/rejig the maintenance schedule to fill the gap. Might shorten the life a bit - but then you're talking 50+ years downline and multiple life extension programs away. One also has to accept the present force has attrition numbers built in anyway.
Just depends how desperately they want to keep the Indians happy and away from going back to buying Russian...