Alter the "My Account" link in installation profile
Perhaps you could use:

hook_menu_alter

Not sure if it'll work with option attributes, but worth a try.

e.g

/**
 * Implements hook_menu_alter
 */
PROFILE_menu_alter(&amp;$items){
  $items['user']['options'] = array('attributes' =&gt; array('target' =&gt; '_blank'));
}


Alternatively, it would be easy enough to add the _blank attr with jQuery.

e.g:

$('body.some-class #user-menu-link a').attr('target', '_blank');


Update: added example PROFILE_ option for menu_alter hook