Well, if the surrogacy thing comes out and proven, the kids are "not of her body" then they definitely won't be in line for succession. It's got to come out for RF to give a reasonable account of why their kids aren't in line of succession. I don't know how else they can explain it away?
But you know being the litigious git the MM is I bet she'd take it to court , arguing their genetic material were use therefore kids are biologically theirs!! What a mucking fuddle
But in all seriousness, the RF needs to take the long view on IVF/Surrogacy etc.. as it is becoming more common place and widely available, they need to have their Royal Legal team take a look at it. What if George or his future partner can't have children the normal route, what then ? sign of the times I think .