On 4.2.0 I've found out that the below code shows the gamercard on memberlist when you paste it in the
Memberlist template.
I have mine after the Avatar. And you must change the field
# to match your gamercard profilefield.
Code:
<td class="{vb:raw bgclass} profilepic"> <iframe src="http://gamercard.xbox.com/{vb:raw userinfo.field#}.card" scrolling="no" frameBorder="0" height="140" width="204">{vb:raw userinfo.field#}</iframe>
</td>