QtWebKit's time is limited now.
Upstream's latest release still uses qtwebkit in media-plugins/mythplugins. I didn't find a reference to qtwebengine in the snapshot for the next release either. I will change the default USE flags to select no plugins by default. dev-qt/qtwebkit will be pulled in only when the user selects a plugin that requires it. I'll edit the installation message to reflect this.
How important are those functions? Are there alternatives?
There are no alternatives in the current mythplugins release. Not all mythplugins use QtWebKit. I expect the next mythtv release to address this. I use mythtv everyday. I do not use any mythplugins on a regular basis. A user must select the plugins desired for compilation, none are selected by default. I am trying to maintain plugin availability for those who do use them.
Providing users with a browser engine with several years worth of unpatched security issues is not a service at this point. The question is not so much if there are alternatives within mythplugins, but if there is any other system browser mythtv users would be able to use, that does not contain those vulnerabilities.
That they aren't selected by default is beside the point; we need to get rid of the dependency.