I'm not sure what the FA can do now, in terms of whether he could actually still be punished for racial abuse. If a court has access to all the evidence and can see it's clearly not enough for a guilty verdict (it's impossible to prove the context of some lip-read words with no witnesses) - then the FA would need to somehow find some new evidence I imagine. It wouldn't make sense for them to come to a different conclusion - and if they did, it would be refuted by Terry/Chelsea and a further legal battle would ensue.
I guess it's possible both Ferdinand and Terry might receive a fine for conduct unbecoming of professional sportsmen, etc. But I don't think it'll be anything major. It's pretty much all put to bed now I reckon.