Old oil begins to thicken and lose its lubricating properties, and it can also accumulate contaminants such as dirt and metal shavings, which will help contribute to engine wear.
If your car is due to have an oil change soon, having it done before a long trip will help to reduce the risk of any problems along the way.
However, if your car is not due for an oil change, it is acceptable to wait until afterward to change it.
Ultimately, it is more important to stick to the recommended oil change intervals rather than attempting to change it exclusively as a preparation for a long drive.