Yes you are correct is saying that Log insight 4.3 cannot be directly upgraded to 4.7
You have to upgrade 4.3 -->4.5 -->4.6 and then finally to 4.7
I have not heard anything of that sort that we can take data from existing LI and use it on New LI .
Its better to upgrade .
Please mark this as "correct" or " Helpfull" if this answers your query.
If you have archiving configured in your existing deployment you can import the archived logs in the new deployment.
This works good if you think you will lose the logs that were collected in the existing deployment.