So whoever owns the properties have decided its not viable so its better to sell the properties. Probably means the yield is too low, probably because, as you have pointed out, they are long term tenants and rent is low.
So the owner decides to sell now as they wouldnt get vacant possession if they waited any longer.
Tenants will now have to move out and pay higher rent wherever they are going.
Any new landlord is going to raise the rents on these places to market rent. So higher rent for anyone who moves in.
And what I find most disturbing is the amount of cheering for the new legislation and rules and regulations that are anti landlord, so anti rental supply, by the very people who this is most going to effect in a big way the next time they move home.
The only hope here for the tenants in this case is for the council to buy the properties. But how many times can the councils do this? The state cant pay top dollar for every property that goes on the market just because it makes the news. At some point they will not have enough money.