Most of it looks good. That said, here are a few things, off the top of my head:
Generally you would want to create backups, although you could use the old server as the "backup" for config files/data-wise.
Make sure to chown all the right directories/files, as needed.
Not sure how distributed the architecture is, or how everything would be configured. I generally advise to use a DNS alias for the Splunk server; that way, if you migrate (as you're doing now), nobody has to update their bookmarks. There may be communications to consider around this, depending on your user-base (and update internal docs, bookmarks, and wherever else you might've documented it).
If you're using SSL, but changing the URL of Splunk, might need to get a new cert generated/signed for it.
If you're using forwarders, you may need to update outputs.conf across forwarders to send to the new box. This may be alleviated through centralized management, such as the deployment server.
Not sure what your security landscape looks like, but make sure that firewalls (local or network), or any other security in place would take into account the new system.
If you're using a separate license server, make sure that the server's added to the license pool. Even if it's all running on the same box, I'd definitely mark it as a "validation" point.
Consider enabling boot-start, if you want Splunk to fire up on boot ($SPLUNK_HOME/bin/splunk enable boot-start).
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