Keep in mind I was just relaying the (looking likely) rumor about Office for iPad. However, I don't believe it will make much difference to iPad sales
Yes, I think so too.
I was instead considering how MS could use Office to foster sales of Windows RT tablets. Yes, very high Windows RT device sales would indeed impact on iPads sales, but I find hard to say by how much, because tablet market is expanding significantly, and there will definitely be room for more than one big player. I suppose the question is more wether or not MS will succeed in being one of them.