I can't give chapter and verse, but from what I understand from this thread (and other similar ones on this forum) the aim is to extend Merseyrail to Skem, with a junction from the current formation somewhere in the Rainford area: it follows that the Wigan service would be cut back to Rainford, but my understanding is that the Wigan service would also be extended to Skem. I don't think that any formal plans have been made, but our consensus seems to be that essentially there would be 2 adjacent single-track lines from Rainford to Skem, one of which would head west at Rainford to Kirkby and Liverpool (and so be operated by Merseyrail), and the other would head east towards Wigan and Manchester (and so be operated by Northern). I'm not quite sure what would happen to a passenger wanting to travel from (say) Kirkby to Wigan - would they have to go up to Skem, change and come back again down the branch, or would they be able to change at Rainford?