I can see MS perhaps making Office time exclusive to RT for a few months, but it's not really going to be a huge long-term advantage.
But that article hits the nail on the head - will MS take away a trump card of its own Surface? I think it's an extremely tough decision to make. The future of computing is moving away from the PC, so MS gaining a significant foothold in the tablet world (along with the accompanying content distribution system and marketplace) would be huge for MS going forward. It might make more sense to wait 2 years before releasing an iOS version. There's absolutely zero risk that businesses are going to switch to another word processing software, so I think the ipad Word market isn't going any place.