I do not know when Grimsby Borough Academy v Ruston Sports will be played. However, although this affects who wins the league I do not believe it affects Skegness Town's promotion hopes.
My understanding is that Skegness Town is the only side from the Lincs League to apply for promotion. As a result their promotion is not dependant on winning the league, they will be promoted as the highest placed applicant.
Which league they will go into is unknown at this stage. There are potentially three leagues Skeggy could end up in: NCEL Div 1 (nearest side would be Grimsby Borough Academy?), United Counties League Div 1 (nearest side would be Bourne?) or East Midland Counties League (nearest side would be Newark Flowserve?). All three leagues have been mentioned for them, whichever it is their nearest side looks to be at least an hour away, hardly ideal at step 6.
What has to be remembered is there are some major changes at step 6 next season with two new step 6 leagues (one in the north west and one in Essex from memory) plus all step 6 leagues have to have a maximum of 20 clubs when several currently have 22 including the NCEL Div 1 and EMCL. As a result there are going to be numerous lateral movements of clubs between leagues across the country.
I was told by a NCEL Board member yesterday that the FA League Allocation Committee is due to publish the step 5-7 allocations on 25th May.