Is it possible to trigger a refresh of the FontView when a master is switched while user is using a smart filter? Currently, we have to enable/disable filter to refresh the view.
You mean you select e.g. the Light master, select a smart filter, then switch to the Bold master, but the cells in Font View still show the Light?
I cannot reproduce. Did you run a script before? Could be that there was Font.disableUpdateInterface() and the script crashed before it reached the Font.enableUpdateInterface().
No, the cells display the correct masters.
Suppose my selected smart filter is “Layer Color Label is Red”.
If I select Light and switch to Bold, same glyphs are still displayed, even though Light and Bold don’t have the same colour sets.
There are several use cases where one would like the glyph set to be stable when switching masters (e.g. to compare things).
I understand, but there are also several cases where we don’t 
Personally, I use a lot of smart filters to check multiple things inside layers. However, I can easily forget to manually update FontView during the use of my smart filters and skip a lot of things.