Tested with ICEfaces 4 trunk r46275, Tomcat 7.042, Tomcat 8.0.15 android 6.0, ipad ios 9.1. The issue as reported is still occurring. Each case was tested on a clean server and browser.
To reproduce you must upload the video.

Nov 24, 2015 10:57:45 AM com.sun.faces.application.view.ViewScopeManager <init>
INFO: CDI @ViewScoped bean functionality unavailable
auxMap: cc=org.icefaces.impl.application.PersistentPart@4d36517d
Nov 24, 2015 10:58:16 AM org.apache.catalina.startup.HostConfig deleteRedeployRe
sources
INFO: Undeploying context [/showcase]
Nov 24, 2015 10:58:19 AM org.apache.catalina.startup.ExpandWar deleteDir
SEVERE: [C:\Servers\apache-tomcat-7.0.42\work\Catalina\localhost\showcase] could  not be completely deleted. The presence of the remaining files may cause problems
Nov 24, 2015 10:58:19 AM org.apache.catalina.startup.ExpandWar delete
SEVERE: [C:\Servers\apache-tomcat-7.0.42\work\Catalina\localhost\showcase] could  not be completely deleted. The presence of the remaining files may cause problems

This is now working when the session expires (and the application server continues to run) via a JSF @PreDestroy event when the session expires.
Will investigate if adding a SessionListener based approach solves the undeploy-time issue noted above.

I cannot reproduce this issue. I tried on tomcat-7.0.56 many different ways and even created an HttpSessionListener, but it didn't do anything differently (doesn't get triggered when the war is deleted from the webapp folder.

I tried with camera first. Took photo and uploaded it. Then deleted war. (within IDE and outside of it, also redeployed within IDE).
Then I tried with camcorder. I get the following:-
Dec 02, 2015 11:45:46 AM com.sun.faces.config.ConfigureListener$WebConfigResourceMonitor$Monitor <init>
INFO: Monitoring jndi:/localhost/showcase/WEB-INF/faces-config.xml for modifications
Dec 02, 2015 11:45:46 AM org.apache.catalina.startup.HostConfig deployWAR
INFO: Deployment of web application archive /Users/jguglielmin/icefaces/servers/apache-tomcat-7.0.56/webapps/showcase.war has finished in 3,857 ms
sessionCreated
Dec 02, 2015 11:45:52 AM org.icepush.servlet.MainServlet <init>
INFO:
ICEsoft Technologies Inc.
ICEpush 4.1.0.SNAPSHOT
Build number: x
Revision: HEAD

Dec 02, 2015 11:45:54 AM com.sun.faces.application.view.ViewScopeManager <init>
INFO: CDI @ViewScoped bean functionality unavailable
sessionCreated
auxMap: cc=org.icefaces.impl.application.PersistentPart@662853ae
Dec 02, 2015 11:47:27 AM org.apache.catalina.startup.HostConfig undeploy
INFO: Undeploying context [/showcase]
Dec 02, 2015 11:47:27 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/showcase] appears to have started a thread named [Mojarra-WebResourceMonitor-1-thread-1] but has failed to stop it. This is very likely to create a memory leak.

Marking this as fixed as the most common use-case whereby the session expires or is terminated is working. If there are some more rare edge-cases that aren't 100% we can live with that since there isn't really a better way to deal with those.