They wouldn't. You would have to wait for the monthly patch tuesday from Microsoft Update.
Guys, this is beta software. It is not a release, or gone gold. It has holes, it has bugs, and Apple want you to test it and give feedback. They can have all their programmers test Safari and miss something out.
1. apple patching process is slower than M$, apple users exposed to the risk longer than M$ users per year, its headline a month ago, do some search u will find it
2. Apple put this BETA out with too many "claims", if its only for the purpose u mentioned, they should have make sure their "claims" be modest and somewhate true. Think about it: apple trash windows whenever they can on TV, then release a "best browser" for windows like a king giving mercy to losers, and turn out the best browser is...... what can apple expect from windows users then?