I don’t know that much about the history of RSS clients, but I’m not sure that Google Reader’s shutdown is comparable to VSCode’s future abandonment in terms of its effects on the market. The crucial difference is that Google Reader was not open source. Maybe if Google Reader had been open source, someone would have kept a fork of it running. I don’t know in what way the RSS reader market was “killed” or why that happened, though, so I can’t say for sure that such a fork would have prevented the market from being killed.

I agree that VSCode is not yet good enough to kill off competitors like JetBrains, so there is little need to worry either way.