I assume that you are actually talking about upgrading just Photoshop Elements and that you have both version 14 programs (Photoshop and Premiere). Yes, you can upgrade to Photoshop 2019 without purchasing Premiere 2019. And I believe you will still get a discounted price if you purchase direct from Adobe.
It will also be possible for you to continue to use your version 14 of Premiere. Each version of the program is totally independent and can coexist on your computer without any problems.
However, I don't think you will be able to load a file directly from the 2019 Organizer to Premiere 14. Although it is possible to use other photo editors with the Organizer, I have never found a way to use a different version of Premiere Elements as a supplemental video editor in the Organizer. But, you can still open Premiere 14 at the same time as the 2019 Organizer, and you can then drag and drop files from the Organizer grid to the video editor.
Do shop around first. You'll often find the full version for sale cheaper than an Adobe upgrade.
Adobe upgrade is currently $US$79.99
Amazon full version of Elements 2019 is US$69.99.
The advantage of an upgrade is that, when you reinstall the software, you only need one serial number. Upgrades require two: the 2019 serial number plus the serial number of the version you upgraded from (which people often lose).
Otherwise full versions and upgrades are identical.