In-place upgrade from 15.3 to 16: available yet?

I've read the installation/upgrade instructions; I've also been keeping a keen eye on the forum updates but it's still unclear: Is there an in-place upgrade from 15.3 to 16?

I loath the idea of a "fresh install" for two reasons: 1) I don't trust dual booting to be properly preserved, and 2) I have so, so many "other things" installed that a simple "back up [your] data, fresh install, restore" does not work. I do a lot of SW and HW development on my Zorin machines; I have a lot of 3rd-party applications and libraries installed - some purposely pinned to older releases - that would result in days of configuration collection, rebuilding, reinstalling, and re-configuring. I would like to avoid that if possible.

I often read in the forums (and elsewhere) where an in-place upgrade is highly discouraged because it is/can be difficult, problematic, or error-prone. The only things I've ever seen cited have been comments that some installed applications may not be compatible with a new OS release. But then that's just as true if I do a fresh install of the OS. If I do an in-place update and something no longer works, I have to install an update; on the other hand, if I do a fresh OS, I'll definitely have to install it anyway. All the naysaying around an in-place upgrade gives the impression that the OS itself could very likely become unstable or unusable - this is something that I just don't understand.

No it is not possible update from 15.3 to 16
Propably it will be with next version Zorin but who know?
I am not developer just user but somewhere here on this forum is topic.

This was never coming from my knowledge, but it may come for 16 to 17. Any upgrade feature will be announced when they release 17 as that is what it will be for.

The only way to go from 15 to 16 is through fresh install.

This very issue, you touch on below:

Exactly.
If you have pinned older releases, you have a high risk that upgrading in place would be quite problematic.
You would have to reinstall those packages to the later release anyway. Which sounds like something you wish to avoid.
Upgrading the system in place would not avoid that, it would force that.

This does not mean that the Direct Upgrade Option for Zorin OS is not any good. All it means is that like much in life: It depends on application. How the user applies things and how things apply to their use.
The short of it is:

There is nothing about performing a Direct Upgrade that could possibly help you avoid this.
A Direct Upgrade is essentially the same as a Fresh Install as far as all the System Files are concerned. The only practical difference between the two is the method used to get from Point B to Point A.
As far as third party applications are concerned, then a Direct Upgrade is quite different. Unlike the system files, these are not necessarily able to fully Bump Up to the next Focal release (For Zorin OS 16.)
When you think about it - it makes sense:
If you do a fresh install, then you must install and reconfigure these applications to suit your needs, right?
If you Direct Upgrade and if that package has a focal release, you may not need to install it. But you may need to go back in and reconfigure it, especially if you pinned older releases. And the really tricky part is - You won't necessarily know what needs configuring. You could be making these discoveries for quite a long while when you go to use an application. You then must stop your workflow... deal with the interruption of reconfiguring it, then try to get back to where you were.
And that is the Best Case, where there is a Focal Release from that maintainer. There may not be... It is better to know this in advance, than it is to cross your fingers and hope.

This is as true on Windows OS, too. Upgrading from Windows 8 to 10 would have troubles with third party apps and a quick perusal of Windows Forums shows users clamoring for help with it.

It's just computing. Sometimes, you can only grab the bull by the horns and show it who the boss is.
Planning ahead, scheduling and creating an outline of what you need and how to get your configurations done can go a very long way toward smoothing the road to success.

Perhaps we can help with this. If you are willing to provide a list of all the applications that will need to be checked for a focal release. This practice itself can be used as double-duty, being utilized as part of your upgrade outline, as well.

Ihe ZorinGroup had hoped to create a 15 to 16 Direct Upgrade path. However, due to the push to release Zorin 16 needing additional contributions to release on time, the plan to have a Direct Upgrade was postponed.
It is now back on track and deep in development with an announcement expected sometime soon. The ZorinGroup has given it Top Priority and yes - a Lot of the development has been completed.

The ZorinGroup follows a "Release when ready" policy.

In the tutorial and guides category you will find a topic on baking up installed software, baking up the home folder (which holds most app configurations) as well as, if you choose, a detailed partition and installation guide.

While this may not be the solution you want, it may be an option that automates much of your feared processes. Read through them carefully prior to acting on any of them.

There will be a release of an upgrade after the ZorinGroup has finished and tested their work. All of the Zorin's software is thoroughly tested prior to release to ensure the least amount of issues that they can provide.