Much of the O365 Excel OM is being ported to JS (AFIAK), but I don't think it'll ever fully replace VBA.
JS in general has taken the programming world by storm in the past 5 years or so anyway. Who'da thought. On the plus side, like VBA, it's very easy to learn. On the downside, it's an extremely difficult language to fully understand the ins and outs of (most JS programmers don't, relying on frameworks and ignorance instead - myself included)