3.5. Priority jumping is deprecated

For a long time, priority jumping was a standard way of moving a call about the dialplan. Specific applications (e.g. Dial()) would elevate the priority by 101 under certain circumstances. This feature is now officially deprecated. Basically, this means that while it is currently still supported, eventually it will be removed. Anyone who continues to use it is making their dialplans vulnerable to failure after an upgrade.
In working with Asterisk you will encounter dialplan configuration examples on the Internet; it is not uncommon to stumble upon grossly outdated examples that use deprecated constructs. In professional practice you should use the most current code constructions and versions of Asterisk. The software is always being updated, but deprecated features are not maintained.
In summary: if you want the operation of your Asterisk systems to be as predictable as possible, keep your code current!