Since when do you need to have a succession plan in the NFL? I don't think that's a prerequisite. It's only discussed because of Coughlin's age. Furthermore if they implode to another losing record, why maintain a line of succession anyway?
The Giants leadership is around the staff every day. If they feel there's someone who has the right skills and mindset to lead the team after Coughlin is gone, he'll get the job. If they don't, they'll go outside the organization. Just like every team in the NFL.
I know it sounds weird to think that the final 5 games will determine a 12-year tenure, but makes sense to me. You don't give up until the full body of work his done. Imagine firing him in 2011 when the team lost 4 consecutive games and were 6-6?
If the team finishes with a winning record and wins the NFC East, they're all coming back and deservedly so, even if the path to get there was torturous, LOL.
I think the close losses plays better for the ideal that they'll retain Reese and change coaches if the team misses the playoffs, but who knows.