I'm not sure any serious gamer is still running 32bit Windows. Last time I came across 32bit on a new machine was on an Atom powered netbook.
Have a look at this LINK Drill down "OS Version" and you can see that Win7 64bit is over 53% of total Steam user. Add another 6 and a bit % from the Vista 64bit users and that's a whole lot of DX10/11 gaming PC's. The guys still running XP can be ignored at this point as BF requires Vista or above. Asking for future games to be run on 64bit machines should be for most people of little concern.
Now the question of thinking that is is a "great opportunity to upgrade to Windows 8" I think most of us have a good idea where MS can stick that steaming pile...
Until they let me disable that Metro BS Win8 can go to hell "I'll give you my Win7 when you pry it from my cold, dead hands!"