Use the category in category view titles

add_filter( 'tribe_get_events_title', 'change_upcoming_events_title' );

function change_upcoming_events_title( $title ) {
    // We're only interested in categories here
    if ( ! tribe_is_event_category() ) return $title;

    // Derive the name of the requested category
    $minimal_formatting = array( 'before' => '', 'sep' => '', 'after' => '' );
    $category = strip_tags( tribe_get_event_taxonomy( null,  $minimal_formatting ) );

    // Build our replacement title
    return esc_html( "Upcoming $category" );
}