Yeah, EA support is key to a successful homeconsole. I think its fair to say that without the likes of FIFA, Battlefield and Titanfall then we wouldnt have seen sales hitting anywhere near what we are seeing now.
In addition, EA are the number 1 publisher on PS4 (or at least, they were). Quite a big deal if you ask me.
As for the question at the end of your OP, I certainly think that 3rd party publishers have that power but only if they are in agreement on the "cause". One 3rd party abandoning a system would be a huge blow, but as long as support is still hitting the machine from other publishers then it will survive. When almost every 3rd party publisher abandons a platform, then the platform has no chance in hell of being competitive.
