Yes, there are plans for this. But you are right that it is a complex problem to solve. at the very least each install would need their own API key to access the data. There is also the issue of end-user agreements for using API data - some do not really allow “caching” of data - but I am yet to fully understand what this means.
It is also difficult to program something like this to function in the background, without someone keeping an eye on the script. There is a potential to inject a lot bad data without any user input.
One option is to provide API integration as “add-on” scripts which you run separately to the web interface. The InvenTree Python API - https://github.com/inventree/inventree-python - would be perfect for this.
Most of these external APIs (digikey / octopart / etc) provide sample python code and this could be linked very simply with the InvenTree python code.
I envision that some sample scripts could be provided and the user just has to provide their own API key.