You can hack it together by making the following changes to qa-feed.php:
1. Change this in the first big switch {...}:
case 'unanswered':
... to ...
case 'unanswered': case 'hot':
2. Add this in the second big switch {...}:
case 'hot':
qa_feed_load_ifcategory('main/hot_qs_title', 'main/hot_qs_title',
qa_db_qs_selectspec(null, 'hotness', 0, null, null, false, $full, $count)
);
break;
3. Finally, change:
if ($feedtype!='search')
... to ...
if ( ($feedtype!='search') && ($feedtype!='hot') )
So long as you've enabled the RSS feed for answered questions, this means you can get a feed for hot questions by substituting hot.rss at the end of the feed URL. It won't show up as a link on the 'hot' page though.