I think GA coming back to do more XF’s is foremost a business decision this time around based on the fact it took so long to settle negotiations. If she was really doing more episodes out of her enthusiasm for the show she’d have come to a decision sooner. Last year she even said she got no fulfilment from playing Scully anymore. I also think she realizes it wasn’t fair to leave the last season on a cliffhanger (thank you very f*cking much Chris Carter).

Gillian doesn’t come back in The X-Files for the love of Alien abductions and stem cells stories. No one is doubting that. But there are many other motivations than only business and money. She said many times that what she enjoyed the most in season 10 was to work with the old crew and with David, so I think there’s that too. I also hope she managed to deal the directing or the writing or both of one episode at least. I think she also does it for us, because of the pressure, because if we don’t get a decent closure, there’s no way she was going to be left alone with that and “allowed” to move on. 

I’m not saying she’s a total philanthropist, no one is in this business, of course money matters, and for now, she can’t get as much money as what she makes with xf with any other show. But money isn’t everything.