India prefers USA as a supplier as it has already dealt with them as is a known entity. Also F16 we will only hve to deal with USA, while for Gripen we have to deal with both SAAB Sweden and GE USA, which will be a headache. Though I personally like the Gripen E over the F16 Block70 with the GaaN AESA, the meteor missiles, etc. Howver, the prototype just flew a few days back, howver a much more modern platform than F16. Both has it's pros and cons.
USAF themselves targeting to keep it till service till 2048
"The U.S. Air Force (USAF) is looking to build upon its forthcoming service-life extension plan (SLEP) for its Lockheed Martin F-16C/D Block-40/42 and Block-50/52 fighters from 4,000 to 5,856 additional hours.
The Air Force
greenlit the F-16 SLEP program in April with the aim of keeping its F-16 Block-40/42/50/52 fleet in service until 2048 by extending the fighter’s airframe life from 8,000 hours to 12,000 hours.
However, in its posting to the Federal Business Opportunities (FBO)
website on June 12, the Air Force increased both the hours required from the SLEP as well as the number of F-16s from 300 to 841." I read it just couple of days back in quwa.org