The USFL has been resurrected and now the XFL going through yet another iteration simultaneously. The success rate of these leagues this century has not been impressive. The XFL keeps coming back, but recently it's been done simultaneously with rival leagues starting up. I do wonder if the chance of success (marketing, financial, and player pool) would increase if the folks running these projects would perhaps pool together their efforts. I think there can be enough interest in spring football out there if marketed and visioned correctly (i.e., a post-college developmental league of sorts that can boast rising talent not yet in the NFL). Pro leagues competing for the same niche space probably won't work (yet again).