Actually I'm in the process of updating an old theme, my current one is 1.4. I'm looking at the readme for 2.3.2 and I'm not sure it accounts for what I'm trying to do. If it does, it's not obvious. Here's what I'm seeing related to this:
ShowHoverState BOOL If this command is present it enables a visual change if the mouse hovers over a button. This command enables HoverButton settings.
"TrackingInterval INT Sets the timer that checks for hover events and OnLeave events. If no value is provided, then the default is 250 (ms).
I believe the first only relates to the graphic image changing when I hover over the task. The second one just seems to time how often it checks for that. I could be mistaken, but I think in both cases, if I simply hover over the task, I'm still going to have a delay before the title is displayed. Is what I'm trying to do not possible with xtaskbar? If so, are there any modules it is possible with?