The good news and the bad:
As you might have read some time ago, Wolfson and Samsung have entered into a partnership:
Woflson Signs Samsung Microchip Deal
Unfortunately, the fruits of that partnership might be incorporated into devices so locked down that Samsung could be ready to make Apple look like Google.
First, there's KNOX, which prevents people from returning to stock after rooting or (therefore) sending their broken phones to Samsung for repairs under warranty:
KNOX is said to be implemented in Samsung's firmware version of the Android 4.3 (Kit-Kat) and will be pushed not only to Note 2 users but to those of you who own the Galaxy S3 and S4.
One source among many
Then there's Samsung's new region-locking firmware which is part of the Galaxy Note 3 and of versions of the S4 sold after July 2013:
One source among many
An article explaining the difference between the carrier lock and the SIM lock
Another article reporting on ongoing issues and problems with using other SIMs despite Samsung's reassurances
Note that the "rest easy" tone of the press release reported in the first article is not echoed by Note 3 owners who report being unable to use their phablets in other regions even after using an unlocking code.
However, there's also this:
How to Avoid Regional SIM Lock Issues
If you've owned other iterations of the Galaxy S, you're probably thinking: "Simple solution -- I'll disable automatic updates under Settings > More > About device > Software Updates." Unfortunately, we don't have access to that option any more. The only thing you can do under Software Updates is decide whether you want to look for an update right now or not. Enabling developer mode (Settings > More > About device > Build Number [tap seven times]) won't reveal the option elsewhere either.
All of which suggests that if you own a S4, S3 or Note 3, you should
root it before your carrier pushes out the update. It's very possible that a ROM will appear which offers 4.3 without Knox. It's also very possibly that developers on sites like XDA will figure out how to disable both KNOX and the region lock. But even if disabling ROMs and fixes don't appear, wouldn't you rather use 4.2 without Knox than 4.3 with?
I'm beginning to wish I'd picked up an LG G2, Sony X1 or HTC One instead of my S4.