Well, I suppose it could happen - but surely, it won't!
The tories were already on the slippery slope in supporting marriage back in the Major era.
I suspect that once again, they are making public utterances that their supporters like to hear but will not follow through.
The other possibility of course, is that they will see it through but in a much diluted form with homosexual partnerships and common law marriages being brokered in because "we need to be inclusive".