If the pandemic ever ends, someone else will buy greyhound's buses out of receivership or whatever and provide long-distance services. As long as there is some demand.
Not discussed is that a massive reason that greyhound failed in canada is that they offered no frills service at the same price or higher than regional competitors. Alberta has a bus line called red arrow that is cleaner, more comfortable, with much better service/experience.
To this day my most miserable experiences on a bus were on a greyhound and I've been on numerous regional bus carriers in Mexico ffs.