You may have seen guidance from people in the WordPress community, telling you to keep everything updated. Of course, doing so could potentially mean new code conflicts that you didn’t have before? So is it worth risking it to upgrade?
While it is true that whenever anything is new, there’s a chance for growing pains, equally, leaving things as they are could expose security loopholes which previously went undiscovered and which have since been patched by upgrades.
The primary reason for upgrading is to stay on top of security. While you may get new features as well, keeping the code secure and patching security loopholes is the primary concern.
Any developer worth their salt will do extensive testing on their code before they ship it to make sure that to the greatest extent possible, there are no conflicts, and if there are, they usually hear about them pretty quickly and they’re fixed in short order.
The benefits of keeping your core, plugins and themes updated far outweigh the potential benefits of not upgrading.
You can improve the situation by only using plugins and themes from well-reputed developers (i.e. don’t install free themes from anywhere but the WordPress repository).
I’d say that upgrading WordPress shouldn’t cause you any concern: the software goes through extremely rigorous testing before any new release. If you think back a few months to the delays in releasing 3.5, it was because the team refused to ship it without first fixing a few annoying bugs that came to light during their testing.
So, just know that upgrading is unlikely to ever cause a big issue, but it will help to keep your site that much more secure. And if something goes wrong, you have The WP Butler to help you fix it.