Normally, Atlassian recommends to upgrade to the latest mayor version number before going to a new mayor number version. This is because upgrades between mayor version are tested that way.
In your case, the path would be to upgrade to 4.3.x before going for 5.x.
You can upgrade directly to version 5.0. Should not be a problem :) However, you can try the upgrade on a test environment first.
You can take a look at this guide:
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG