Office for iCloud is up to MS. IIRC there are APIs that developers use to open up this functionality. I wouldn't hold my breath though, MS are slow to update office and only make it 'good enough' IMO and not as good as it could be.
As for iWork, I have no idea if Apple will port a Windows version. Seems like a good idea to me if Apple want iCloud to gain traction but I doubt that iWork would get much support from Windows users. Who knows?