Sony has no reason to do it so I don't see this happening.
I'm not against it, I'm just trying to predict the outcome.
I'll be surprised if Sony gives in and allows it but it could happen anyway.
Sony has the biggest console player base, and they use that to attract most customers towards the PS4. That is one of the current strengths of the PS4.
For example:
If your friend has a PS4, you are more inclined to buy a PS4 to play online with him, if there were no barriers, that upper-hand Sony has would banish and it wouldn't matter if you get an Xbox or PS4.
Of course this would help Microsoft a lot while hurt Sony's sales in some way.
I don't see any benefits that will help Sony in any way so I don't think it will happen.
And if you think it's only 1 game, think twice. This would open the floodgates to many more companies asking for the same treatment, and helped of course by a public campaign led by Microsoft for obvious reasons.