Probably no one can commit or predict a lifecycle of the current models. But you can look back history.
FG100E started with 5.4.1, which was released June 2016.The rest is explained in@Yurisk 's website. (at the bottom ohttps://yurisk.info/2023/01/03/fortigate-end-of-support-end-of-life-cycle/)
EOO(end of order) came in Aug 2021, which means it reaches EOS(end of support) in Aug 2026.
So total span of life would be about 10 years. I would expect similar for the 100F. I think 100F became available a couple of years ago if I remember correctly.
Toshi