What about building web parts which take into account the fact that Office 365 is global, and many of the organizations that use Office 365 services operate in many different languages? In Chapter 3, Getting Started with the SharePoint Framework, we already looked at the files that make supporting multiple languages possible. It is very nice that those files are built into Microsoft's Yeoman SharePoint scaffolding, but it is down to us as the developers to use them.
If you know that the web part you are building doesn't need to support multiple cultures, then you can ignore the following. You can write all text in English, French, or whatever language you want. However, if you have reasons to believe that the web part needs to support more than one language, you should build it to do that from the beginning.
This doesn't mean that you need to have translations for all of your text from the start. At the start, you probably don't even know what to translate...
