KevV: I don't think it [F-35] was seen a F-16/F-18 "replacement" so much as a replacement in those aircrafts size class....
I believe the JSF program was absolutely touted and understood as a "replacement" in the original JSF program specifications, program of record, and literature without any qualifiers about size class.
The JSF program was touted as a replacement for the F-16, A-10, F/A-18 A-D for USN (and perhaps USMC), AV8B and UK Sea Harrier/GR7/GR9 and Tornado GR4. Also specified to complement F-22 and F/A-18 E/F.
https://apps.dtic.mil/dtic/tr/fulltext/u2/a472773.pdf