PhotoVia will pick up the changes quickly. The exact timing depends on a couple of factors. First, how many photos are in the upload queue ahead of it. The photos are sorted by capture time with the most recent photos getting updated first.
Usually this is what you want as it is common to work on your most recent photos. Even if there is a long line of photos that still need to be published, if you modify a recent one, it will go to the front of the line.
Second, it depends on when Lightroom saves the changes to your lrcat file. Usually this happens within a second or two of when you make edits but I have sometimes seen it take a minute or more. This usually happens the most quickly when you are in the Library module in Grid Mode.