Don't think it will happen though, didn't Jim say no more kids for Harry?
JB also said, more than once, that he wasn't going to kill Karrin or power her up. He sometimes changes his mind, and sometimes his hand is forced by the flow of the story.
Not saying I consider Harry/Lara as parents likely, but I wouldn't absolutely rule it out, either. Not when it could cause Harry so much worry and grief.
(I wonder, if Lara did fall pregnant with Harry, would she want the child to escape White Courtdom, or would she be fighting against Harry to make sure her child was immortal too?)