Seebz

Improve Page Permalinks. 
This plugin just adds .html to the permalink pages when needed. 
An option can prevent this action for specific pages.
<h4>Example</h4>
<ul>
<li>yourblog.com/page.html</li>
<li>yourblog.com/parent/</li>
<li>yourblog.com/parent/child.html</li>
</ul>
<h4>Compatibility</h4>
Not tested yet with all previous 3.0 WordPress version
Tests OK with the following plugins
<ul>
<li><a href="https://wordpress.org/extend/plugins/permalink-redirect/" rel="ugc">Permalink Redirect</a> (v2.0.4)</li>
<li><a href="https://wordpress.org/extend/plugins/cms-tree-page-view/" rel="ugc">CMS Tree Page View</a> (v0.6)</li>
</ul>

Improved Page Permalinks

Improve page permalinks by adding ".html" for final pages

Nicolas Korobochkin

This plugin transforms default bbPress permalinks (URLs) that use slugs into permalinks that use numeric IDs.
Please star the <a href="https://github.com/korobochkin/bbpress-permalinks-with-id/" rel="nofollow ugc">GitHub repository</a> to support continued development of this project.

Permalinks with ID for bbPress

I will try it

Transforms default bbPress permalinks (URLs) that use slugs into permalinks that use numeric IDs.

Improved Page Permalinks vs Permalinks with ID for bbPress