Exactly this. Lots of people cancelled their fixed lines (a lot of which weren't used for broadband) due to the MNOs. Now they're actually gaining fibre customers and will continue to do so. Far from "dying".
They're actually not gaining fibre customers, not at the rate they are losing copper lines. Most of this stems from the layers of legacy bureaucracy and incompetent staff which are difficult to shed.
Even if you really really want to do business with Telkom and use their services it's next to impossible. They lose orders, they have month long internal bickering sessions about who's job it is to install someones fibre, and by that time the consumer lost interest and went with Vuma/CellC/LTE.
I was pleasantly surprised this morning from a very pleasant and well spoken lady from Telkom asking me about a complaint I’d logged yesterday re my slow/intermittent 10 Mbps ADSL line. As i started to list my problems she said that they were aware of problems in my area yesterday and they had been resolved. I normally get about 9.5 but yesterday in was either 0 or slow like 1.6. This morning it started at 9.6 then went off completely, however, it’s back to normal now. Hope to get fibre in next 6 months.