Square Enix has been bringing lots of its classic games to the PlayStation 4 lately, and apparently it's part of a company-wide ambition to make its entire library digital. President and CEO Yosuke Matsuda confirmed that it's something the publisher is exploring in an interview with Game Informer, but it's not settled on how it's going to get all of its games out there. We'd also have to consider whether or not it will work well exclusively including our own catalogue titles.
With Microsoft, EA, and Ubisoft all touting the strengths of their subscription services, it sounds like Square-Enix is considering their own system as well. "That is a request that we hear often". If they get enough older, never-before-on-PC games, I'd definitely be interested. The more classic titles that you might have played on NES, we are still working hard to make it so you can play those.
Google's Stadia has ignited a firestorm of discussion involving the possibility of publishers making their back catalogs available through a subscription / streaming service.
"I'm embarrassed to admit it, but in some cases, we don't know where the code is anymore. Sometimes customers ask, 'Why haven't you released that [game] yet?' And the truth of the matter is it's because we don't know where it has gone".
As Matsuda pointed out - and as Square Enix has repeatedly acknowledged in the past - one of the barriers to creating such a service is obtaining the source code for old games.