1) You need to update the files in the primefaces package path:
src/main/resources/META-INF/resources/primefaces/fa/FontAwesome.otf
src/main/resources/META-INF/resources/primefaces/fa/fontawesome-webfont.eot
src/main/resources/META-INF/resources/primefaces/fa/fontawesome-webfont.svg
src/main/resources/META-INF/resources/primefaces/fa/fontawesome-webfont.ttf
src/main/resources/META-INF/resources/primefaces/fa/fontawesome-webfont.woff
src/main/resources/META-INF/resources/primefaces/fa/fontawesome-webfont.woff2
2) Edit the file src/main/resources/META-INF/resources/primefaces/fa/font-awesome.css and change to:
src: url("#{resource['primefaces:fa/fontawesome-webfont.eot']}?v=4.7.0");
src: url("#{resource['primefaces:fa/fontawesome-webfont.eot']}&#iefix&v=4.7.0") format('embedded-opentype'),
url("#{resource['primefaces:fa/fontawesome-webfont.woff2']}?v=4.7.0") format('woff2'),
url("#{resource['primefaces:fa/fontawesome-webfont.woff']}?v=4.7.0") format('woff'),
url("#{resource['primefaces:fa/fontawesome-webfont.ttf']}?v=4.7.0") format('truetype'),
url("#{resource['primefaces:fa/fontawesome-webfont.svg']}?v=4.7.0#fontawesomeregular") format('svg');
3) Unfortunely you need to add all new icons manualy in src/main/resources/META-INF/resources/primefaces/fa/font-awesome.css as these two samples bellow:
.fa-handshake-o:before {
content: "\f2b5";
}
.fa-envelope-open:before {
content: "\f2b6";
}
For a complete list of icons added in 4.7.0 version take a look at this commit https://github.com/primefaces/primefaces/commit/b40b2fd5a27956d49d247b24c8aac60a8a3301eb
There are some questionaments why this is so difficult to update and maybe in the future it's become more simple https://github.com/primefaces/primefaces/issues/1956