I fail to see how putting these games on another console, where more users will be able to play it, could negatively impact sales. It's not as though people who have PS4s are going to look at it and say "OMFG it's on Xbox One as well, I'm not buying it!" regardless of how bad that system is...unless they're complete and utter morons, anyway.
But seriously, they're not going to give a damn either way. A lack of exclusivity doesn't stop people from buying games altogether; it allows more people to play them. Perhaps the cost of bringing it to the system could outweigh the benefits, but somehow I seriously doubt that is going to be the case; Xbox One deserves to crash for its draconian policies, but that isn't going to happen. When more people can access it, more can buy it, and therefore more money is made. It's not rocket science.
But I think the choice is clear either way. Buy it and own it and do whatever you want with it on PS4, or license it and never own it on the Xbox One. If you have to think about which of those two options is the better one, then you clearly don't have the intelligence necessary to play the game in the first place.
It can negatively impact sales because it costs them extra money to make a game on more than one console, and if they don't make that money back in sales then they've made a loss, which is obviously negative to their sales. What you're saying would be sensible if they could create a game for all systems without extra cost, but they can't. These things cost money, and they only get money back from sales, and if they put a game onto a platform where the sales aren't good they are taking a big risk that they might make a loss on it.