Can I extend entries listing views (currently or in the future)?
The current answer to this is no, not out of the box.

The unofficial answer to this is, it has been discussed several times out there in the forums and there are some good arguments to make that this is a core part of 'content management'.

The developer-friendly answer to this is yes, you can control those columns if you create a plugin with a new Element Type.  Your Element can extend the default Entries Element Type and customize the columns in the listing views.

Within your Element Type:

defineTableAttributes() - Returns the attributes that can be shown/sorted by in table views.

modifyElementsQuery() - Modifies an element query targeting elements of this type.

getSources() - Returns the element type's sources and can be used to trigger filters on the table view.

You can create a new listing template with these three lines of code:

{% extends "_layouts/elementindex" %}
{% set title = "Page Title"|t %}
{% set elementType = 'PluginName_Element' %}


Is this a smart thing to do?  It probably depends on your use case.  Elements are powerful, but they also take time to develop and maintain.  While you can easily extend a class, several parts of the Control Panel UI are not as easy to extend if you start adding variations on the intended use cases. Make your case to P&amp;T about this feature being a core part of content management and if enough others do the same, you may save yourself a lot of custom development.  I think there is a strong case that this type of feature can only be done well in the core.