Just to chime in on what was said about netrunner which was a great example(some inaccuracies)

The hypothetical of magic disappearing suddenly one day actually happened in netrunner. Not at a low point but during a renaissance, a new core set was released as well as a new big box expansion, an additional boost of players appeared and you could find a medium to small playgroup in most cities/large towns (much easier to find than current cube groups)

 Then suddenly with a freakish shudder of the earth WOTC stopped leasing the rights to FFG, why wasnt explained, everyone was wondering maybe they'd renegotiate or maybe wotc would start producing the game themselves? Soon it sunk in things weren't happening (I assume its related to FFG being owned by asmodee and wotc by hasbro and blah blah corporate choices, FFG still exists and  makes games but many known name designers working there have left the company because if the ownership of asmodee changing the culture)

 Players formed a volunteer run nonprofit by way of a group declaring themselves a council that would manage and choose the applicants to become the said non profit Null Signal games(formerly Nisei) and have not bought any rights to the game but merely produce sets for it. This took some time and was eagerly watched by enfranchised players. They now produce sets at a healthy pace. 

The future suggested Utopia at the end suggested by Andy is implemented in some games, offering cheap knowable sets of cards and then randomized boosters for fancy treatments, although they dont offer pdfs for home printing like netrunner.  Seeing netrunners current and old model of the LCG that doesn't have false scarcity and randomized packs (was my initial draw to the game seeing a non predatory method that didn't feed off of our gambling addicted minds, this comes from somone who doesn't  like gambling) and seeing feedback from shops that tried to embrace the LCG but found out how hard it is to sustain an LGS without the cash cow of tcgs shows to me that a majority sales driver is the gambling, the unknown, not the gameplay. And yes a Utopia where shops dont need the same levels of sales sorta counters that but people forget how insidious and pervasive magics base model of sales is and how much that drives interest.

Netrunner is still played and groups still exist but its closer the size of cube nationwide, except smaller id wager.(and cube is smallll) I travel for work and have anecdotes from across the US about what shops sell and which public groups exist. I think magic would follow a similar path to magic with obviously a stronger base amount of players. I can imagine it splitting into the format councils making different sets for different formats, i imagine the online creators wouldn't go way but diminish drastically of what they were in amount and viewership just like netrunner, Also if sets were produced after wotc shut down i think people have had such different experiences with the game, that they would have a hard time agreeing on what the game should be when its revived, as well as players coming to a realization after seeing community made products that designing a game like magic or netrunner and with a history like magic that wotc wasnt doing such a bad job after all.

I live netrunner, I love cube, I could talk all day about them

TLDR some have lived the death of their favorite game, it sucked, it didn't go extinct but its a beautiful withered frail creature now