Unfortunately for Overwatch, a battle.net account / connection and their centralized servers makes it a far harder task. They've moved toward a model where the reverse engineering and ingenuity involved to get it to work outside of their control is increasingly prohibitive.
These things often take volunteers hundreds of hours to figure out and are illegal according to terms of service agreements (followed by lawsuits no less--if you look into "bnetd" and "fsgs" starcraft alt servers, and WoW bots, Blizzard is not afraid to go this route). If it's just too much work for said hackers, it likely will not get done, especially if legal action against the volunteers is a probability.
There is also quite some history showing that DRM-content providers do go under, and people do lose access to their "purchased" (rented) items.
Nevertheless, there are sometimes happy endings, and I'm reminded of this comment [1] by Don Hopkins just over a week ago highlighting the importance of equal parts archivists' duties, detective work, and persistence (very much worth reading) with a healthy dose of luck. Unfortunately, this is probably more an exception than the rule, though older/niche games are perhaps more likely to survive through such efforts than popular ones (Carmageddon's resurrection with the new Stainless comes to mind) given that there's less at stake.
If a much more popular franchise goes belly-up, I would be exceedingly surprised if independently playable versions were ever released. More likely, you'll see new installments based on the same IP with the same shortcomings, thus repeating the cycle. Tribes is a curious, if complicated example (failure, resurrection, failure, resurrection), but it's also a case where an interested third party was able to circumvent the authentication server code (Tribes 2 via TribesNext).