"One-off deal as relief for summer 2022: rising energy prices, pandemic relief."
I get why drivers might need a price break with the latest gas prices. Consumers of public transport in Germany, OTOH, have not experienced big bumps in ticket prices; this dramatic price drop will surely be welcomed by consumers, but actual energy costs will remain high and will be absorbed only temporarily by transport providers. By September 1, there'll have to be a "reckoning" of some kind.
According to this article from 4/27, some states are threatening to boycott the whole deal. Saxony, Bavaria and Baden-Württemberg are having a public Kuh about the financial and logistical burdens imposed on them by the federal government, which they say is underfunding them. Besides the loss of ticket revenues that everyone foresees and ever-rising energy costs, they're dealing with general inflation and with increased ridership costs (Ukrainian refugees already ride for free) and will need additional train cars, security personnel, etc. to handle the anticipated onslaught. Some expect DB ticket sales on the IC, ICE etc. long-distance trains to suffer as thrifty customers opt for time-consuming trips on the slower trains using their 9-Euro ticket. B-W's transportation minister foresees a huge overall increase in ticket prices after the 90-day period is up. At some point, somebody will have to pay for all the summer freeloading, and unless there's a bunch more money coming out of Berlin, higher-than-ever ticket prices - and a large drop-off in ridership - will be the result.
Are the 9-Euro plan and the Schönes Wochenende Ticket comparable? Well, the S-W was a DAY PASS, not a MONTH PASS. When the S-W was discontinued, the price was €44 - €68 for 2-5 people. It was not uncommon that multiple groups of 2 couples or 4 friends would travel together, so at just €15/ each per day, in a time of normal economic circumstances, the regional trains were pretty packed on Saturdays and Sundays whenever the weather was good. And this crowding was part of the reason the S-W ticket went away. But when everyone living in Germany and every tourist in Germany can get a 30-day pass for just €9 during the summer travel season, and when many rail authorities in Germany are predicting "chaos", I would NOT expect the crowds to "normalize" starting on June 14, especially when you take into account how long people have been cooped up by this pandemic. The ticket lines will be short. But on the platforms and in the regional trains I think you should expect to be elbow to elbow. IMHO, this is not your grandfather's S-W ticket!