For some definition of "will", I guess. It's part of the windows logo requirements for x86. For now.

But what happens when someone screws up? I buy a laptop with a windows logo and try to install OpenBSD or whatnot, only to discover that the "disable secure boot" option is missing or broken. What's my recourse? Wait for a firmware update (which we know from experience will never arrive -- it boots fine in windows)? Return the laptop (which works perfectly within its warranted behavior)? Whine and look sad?

The incentives are all wrong for this to be a stable situation. Over time and platform changes, "disable secure boot" is going to rot. We all know it.

Also, we don't want secure boot as ARM moves into the more mainstream device space. We want Linux on ARM machines just as much as on x86. M$ is intentionally driving ARM boxes without the ability to change the OS to try to stop that inevitable growth.

Shop more carefully?

Well there will be some incentives for the manufacturers who do NOT support SecureBoot: they will get a better share on the market than their current one.

Sadly, that isn't enough. For everyone who understands how UEFI limits their freedoms, there is a dozen people who will say "look! shiny!".

Idiots will always outnumber smart people. Microsoft relies on that.

Well the 4% share (or more) of future linux users who need a reliable Linux-PC is not so small if you consider the potential number of clients.

Surely some will take advantage of this situation, if everyone else rushes to have SecureBoot.

Who cares? There are going to be millions if not billions of Secure Boot ARM devices manufactured. x86 doesn't make this not a problem.