You may now switch weapons on your own time and not have to bring up a menu to do so.
Today, Hajime Tabata, the director of Final Fantasy XV participated on the official forums and gave fans information about the new real time weapon switching system. You can find his official post right here: Official forums
The new real time weapon feature maps all 4 weapons to the up, down, left, and right buttons on the PS4 dpad. Tabata says you should be able to switch between them in real time.
This change makes the “Break -> Rush -> Slash” system change so that weapons will not switch automatically during normal, consecutive attacks. It has now been designed so that you can attack consecutively while switching between the main weapons you pre-set in real-time.
As for attacks like the “Counter” and “Raid (Jump Attack),” or attacks that the player can unleash at specific times, you can use main weapons if nothing is set, but can also automatically switch to weapons intentionally used for these attacks like the demo, as well.
It looks like Tabata and the development team will continue to give further updates on Final Fantasy XV on the forums/ future Active time reports.
Source: Gematsu