Is my only option to get it (Tomcat 8) running locally outside of Eclipse and maybe hook a remote debugger into it for stepping through code? Will that even work for Eclipse Kepler + Tomcat 8? IntelliJ IDEA 12 couldn't do it in the 30 minutes of time I put into that path. the Tomcat 7 adapter doesn't work, and it doesn't look like there's a new extension for it to download in the 'Install new Extension' dialog. In Eclipse Kepler though, there is no supported adapter in the add server list for Tomcat 8. Update 2/27/14: 8 is released now, and adapters built for WTP, just not integrated into eclipse bundles yet.
Now there is a RC version on the main Apache Tomcat page. Tomcat 8 is still in development, but you can get it here. EDIT : Eclipse Luna is here, and support for Tomcat 8 is included in the bundled WTP : ) Happy days!