When the FL assesses the impact at the end of the season, they will have to take a look at the numbers TF gave them and the reality at the end of the season. Of course I could be wrong, but from the propaganda TF has dished out, I would summise that he told the FL that initially the gates would be low, but after a few weeks rise to around 3k, and again assumption, but will have said they will be approaching full gates by end of season! On those figures, then I would assume the FL backed their decision (as just under 8k when gates were around 10k at the ricoh isn't too much of a drop).
However, if the gates fall consistently under 2k (and may well be under 1k on those chilly midweek nights), then they will have a virtually impossible task of convincing anyone (even the spineless ones at the FL) that sixfields is viable.
There are still things fans can do, but it will be a long haul. During that time there is no doubt their stooge will ensure that only pro-sisu callers will be allowed airtime (this is a minor inconvenience, but still disgraceful from the beeb to allow it). NOPM - this is the main part. Assuming the fans will stay away (as i doubt many more than the core away fans will go anyway) whilst sisu might have funded it, it will be hard to justify when they produce their projections for the next year! Thirdly anyone in nearby councils must put pressure on their respective councils to block any move to build a stadium!
Whether fans will do any of this is debatable, more likely ccfc will die off through indifference once the "novelty" of going to a shed 35 miles away has worn off!