I'm pretty sure the future 11.4.0-37 update WILL block arm9loaderhax, meaning that Homebrew that is ARM9 only (such as Hourglass9, Luma3DS menu and Decrypt9) can still be loaded, but anything else that uses ARM11 (such as the Home Menu and other Homebrew) won't boot at all. Because they will implement FIRM0 and FIRM1 checks, which still scan the files in FIRM0 and FIRM1 to determine if their MD5 hash matches, and if not, it will refuse to boot ARM11. It will also check for any extra files in FIRM0 and FIRM1, if it detects any payload files other than the ones that are permitted, it will refuse to boot ARM11.
When that happens, there will be no way for even Luma3DS to disable the FIRM0 and FIRM1 integrity scanner, since it's an ARM9 function (in which is already initialised). So unless sighax is released (which will allow access to ARM9 functions), we'd be stuck with nowhere to go, except to tell users NOT to update to 11.4.0-37.
So we have to be prepared for this, which will be bound to happen in the next update, no doubt about it. We have to be ready to release sighax before Nintendo patches arm9loaderhax.
Not to also mention that they will patch soundhax in the next update too.