Oh no, not ominous at all ... look for this list of three choices being reduced to the first two. Coming soon.
Overnight they'd lose many thousands evangelists and unpaid tech support staff (ever help a family member with their Mac?).
Like with iOS? Hackers will be annoyed, but Apple doesn't care about them when there are more than enough developers who are either in it for the money or who agree with Apple's position.
However, from Apple's perspective, if there are "enough" developers who can't or won't leave (because they develop Mac software or iOS software or both), Apple might not care if you do.
And it's not like the signing process is particularly onerous -- it won't represent even the slightest barrier or inconvenience to shareware, freeware or open source app distribution.