No sucking involved
If MS distributes SuSE Linux, and that contains some GPL3 code, then MS is bound by the GPL3 for that code. There is no loophole.
Code distributed under GPL2 or earlier is indeed unaffected, but as was pointed out above, many open source licences state GPL2 or later. So MS could be in trouble with them too.
MS only have a problem if they don't want to follow the licence conditions of the software they're distributing. The GPL is very fair in this respect as it grants the same right to the recipient as to the distributor. Of course this doesn't fit in very with with MS's business model of End User Licences and retaining control even after you think you've bought the software from them.
Also, as pointed out above, MS already distributes GPL2 code (gcc etc) in violation of GPL2 because it doesn't make the source code available, and that's just the stuff we know about. In their closed-proprietory model in is almost impossible to say what other violations may be going on unseen. This is why there is a fuss about SuSE Linux and GPL3, because we can see it. Microsoft don't like this. What does that tell us about their motives?