Of all companies who could make a football comeback, I think it would have to be 2K or Natural Motion only because they have an IP that would be easiest to work with. The problem, is all the money that goes into research/discovery, strategy, developing, testing, marketing, etc. and convincing a company to invest it in a sub-genre that hasn't been to fruitful in the marketplace (see: APF2K8, Backbreaker, Blitz: The League, etc). It is a huge task and financial burden to develop games these days and with that I simply don't think many companies are willing to put themselves at risk to develop.