Going directly to 7.0.7 should not be a problem. The extra steps are usually only needed to upgrade between major releases. (And I think it's less of an issue with the Universal Forwarder, than it is with the full version.) For example, Splunk Enterprise below 6.5 needs to be upgraded to 6.5.x before upgrading to 7.x, but 6.5.9 is fine and you wouldn't need to go through 6.5.0.
So in your case, upgrading directly to 7.0.7 is fine.