It's definitely an interesting change. Charging a high fee is pretty crazy and will likely frustrate many smaller devs enough focus more of their energy on itch.io (maybe they'll see it as a way to raise the first 5k). We've seen a lot of support on Twitter & reddit in favor of itch.io since the announcement. Alternatively, since they're making the only barrier to entry a payment then it makes me wonder if many larger and more financially motivated developers will end up skipping itch.io entirely. But with Steam getting more and more games, we may see more people posting here regardless to get access to more exposure through a different audience. itch.io also provides refinery, which is something Steam isn't doing. At the end of the day I want itch.io to be defined by what is unique about it, and not what functionality it provides that is available elsewhere. So although this update to steam may change the game dev ecosystem, I'm definitely not worried about the future of itch.io
Since there's only speculation about the price though, we'll have to wait and see what happens.