No, presets are stored in a dedicated patch storage area that is not touched by the update process.
Minor firmware releases (m.n.0) where the second (n) digit changes may have audible changes as we fix problems (removing distortion, etc.), but we make every effort not to affect the sound of existing presets. The CHANGELOG.txt file in the update package will list any changes that affect the sound.
Patch releases (m.n.p) where the third (p) digit changes address functional issues and will not affect the sound.