The next version of JSP specification is not published yet, but my expectation is that the new set of Java EE specifications will target Java 8. One place that we forgot to update when switching Tomcat 8 Jasper to Java 7: \java\org\apache\jasper\resources\LocalStrings[_lang].properties The help string there still says \ -source <version> Set the -source argument to the compiler (default 1.6)\n\ \ -target <version> Set the -target argument to the compiler (default 1.6)\n\
I did a global search in Tomcat 9 for "1.7" and fixed all the references I found. I've also fixed the JspC usage message in Tomcat 8. That fix will be in 8.0.16 onwards.