There is an upcoming digital product called Magic Next (most likely a code name). No one knows for sure what it is but the rumor is it will be Magic Online but for a monthly fee you can play with all of the cards.
There are programs out there that do this now but this would be official and would presumably have the full rules enforcement that MTGO has.
If true and assuming it was priced reasonably (I am guessing there would be tiers of service depending on what formats you want access to), I would love this and would probably pay.
Theoretically, maybe, but probably not. It’s common for players to complain about the cost of acquiring cards to be a barrier, and it is. But more importantly, it’s also the way to maintain a playerbase and to hold competitive interest. A huge amount of the fun is in hunting down the cards you need and acquiring them. The sense of pride and ownsership is vital to having a strong, invested group of players to keep the game alive.
There are already ways to play for free. Programs like Apprentice and its various successors have been around for a while. Playing against strangers on there is about the worst possible version of the game. Or consider the beta version of Magic Online. Drafts start constantly, but most players drop out midway through or never play their games out. It’s awful when there is nothing financial on the line.
It’s hard for me to imagine a full version of Magic on a subscription model that would be a good, sustainable experience.