This should have no impact for the vast majority of viewers.
For most viewers, this should have no functional impact. However, an extremely small percentage of viewers—less than 0.0001% of all views—use a version of Internet Explorer that identifies itself as IE9, IE10, or IE11, but fails to parse ECMAScript 5. Viewers using that kind of browser will no longer be able to play Wistia videos. Currently, we only know of one uncommon configuration of Sharepoint that leads to this situation. For Internet Explorer 8 and below, as long as we can identify it as such, we will continue to serve the ECMAScript 3+ compatible player scripts.
If you are operating in a business that runs a modern version Internet Explorer configured such that it cannot parse ECMAScript 5, we urge you to update your settings so that we can deliver working scripts to you automatically. We've reached out to some folks directly where we've identified potential issues, but if you have further concerns or questions about this, we may be able to help you out; send email@example.com