I just successfully upgrade one of our test sites 4.6.2 --> 4.9.0 --> 5.2.2 without any issues.
On the main portal it has 8 pages 10 users, blog module and the forum module installed
On the child portal it has 5 users, forum module and the Events module installed
The site uses the default Extropy skin
I have not checked every possible user/module combination but after the upgrade I was able to log in as Host and Admin and a blog user and there were no upgrade errors in the site Event Log
There is 1 issue that you'll likely run into when you attempt to sign into the site the 1st time after upgrade.
It's logged in Gemini currentlyas a DNN Pro bug.
The detail and workaround is as follows:
You won't be able to log in... you click the Log in link and nothing happens or you get a JQuery error.
Close your browser clear all cache and cookies, revisit the site and at that point you should be able to log in.
CAVEAT:
There were no 3rd party modules installed on this test site.
If you have 3rd party anything on your site please check with the vendor for 5.x.x version compatibility before you upgrade.