Windows 11 will work on older models but it will not be a FREE upgrade.

A lot depends on how old the system and the specs. As an example I have a Latitude E5430 with a gen 3 CPU, TPM 1.2, and SecureBoot and am running the Beta Channel most recent build. It is stable and fast and I have yet to see a problem. But there are others with older hardware that are having trouble. So in a manner of speaking it may be luck of the draw.

And I totally agree with your statement regarding update vs image download. With a non-compliant system, update will not allow a user to do an install. But with an image download there is no problem but I believe the user will be warned that the system does not mean system requirements when installing from the image. It will install just fine though. Now MS has stated that unsupported system will not receive Windows 11 enhancement updates but will be able to install security updates and fixes. A lot yet to be resolved and MS has changed direction on this more than once so the RTM should be interesting.

And correct me if I am wrong but free upgrade meaning you will not be able to update to Windows 11 but can download and install the iso image, but there is no fee for doing so. I was a bit confused by that.

@JOcean 

" download and install the iso image, but there is no fee for doing so. I was a bit confused by that."

You can download and install but NOT  ACTIVATE.

This is the status quo for 10 currently. You can install but not activate using the "I don't have a key option."

I have not seen that. Could you give me a source as that is very interesting and I would love to read it.

Sorry I was not clear there, I meant regarding Windows 11 not 10.

I can't give you a source for Windows 11 since its not released yet. For windows 10 this is well known for several years.

To check if your computer is activated;
Right click Start, click Command Prompt(Admin)
Click Yes to "Do you want to allow this app to make changes to your device"
enter slmgr /xpr Then hit the Enter key
It will tell you when it expires.

If it is not activated then you will have to buy Windows.
If it is activated as Windows 10 Home $119 or Pro $249

OEM system Versions are less expensive but do not come with support from Microsoft.

win10 64 recovery DVD no license key

I recommend you buy this DVD NOW because once they are gone they will NEVER be available again.
https://www.newegg.com/recovery/p/N82E16832350238

I personally don't want Windows 11. I'm hating 10 as it is. I'm well on my way to having a decent grasp on Linux, at least enough to be a competent user and a lot of it isn't much different than Android coding so I don't think it will take me too long to be able to manipulate the OS to get rid of things that I don't need or care to use. There's plenty of good developers in that community for things I may want that aren't included and if it's not there all one has to do is ask and they will either come up with something or tell you what you need to do it yourself. I have 2 official product keys for Windows 10 Pro. Both of my laptops came with Home edition but during both upgrades I purchased Pro for clean installs on both of the new SSDs. I have updates blocked on both laptops, I pop on once a week or so and download the ones I need manually so that they can't force it upon me. I believe my older one isn't supported so that is going to become my first Linux Mint machine. I'll keep Win10 on the newer one until I am ready for my next laptop which is looking like it's going to be either an Asus or possibly an MSI. I'm keeping an eye on them. It is probably at least a year out so I'll see how they do until then.

Windows 11 Version 21H2 Maintrack is due to be released next month on the 5th of October 2021. This means Windows 11 should be made available to the Release Preview Channel very shortly. There is unlikely to be any significant changes to Windows 11 Version 21H2 Maintrack from the current Windows 11 Beta Channel Insider Preview especially in the fundamental areas of Microsoft Product Activation and installation/driver support for hardware...

Recently Microsoft have split system requirements into a green (all requirements satisfied), yellow (the Processor model and/or TPM 2.0 requirement are not satisfied) and red category (not supported).

Currently the Windows 11 Insider Preview Beta Channel ISO installs and runs fine on systems with 6th Generation Processors and 7th Generation Processors which are in the yellow category. I have it running on an OptiPlex 7040, OptiPlex 7050 and XPS 13 9365 without issues and on the driver side, Dell Command Update works as expected on a clean installation of Windows 11.

The statement Microsoft made regarding system "not receiving future updates" is likely to reference major future Feature Updates and not minor Quality Updates. They have recently moved the Windows 11 Dev Channel away from being a testing ground for the upcoming Windows 11 Version 21H2 to begin work on the next development of Windows 11 i.e. towards the next Feature Update.

In the Windows 11 Insider Preview Blog, for the next Dev Build they have reiterated that systems which meet the yellow level of system requirements will (at least for now) continue receiving Windows Insider Preview Builds however they will have a yellow notification in the Windows Update → Windows Insider Settings, that the PC may not perform as well as expected and may have issues that Microsoft may not fix. The systems that are at the red level and currently enrolled in the Dev Channel, will instead get a red notification warning saying the PC is ineligible for the Windows Insider Program, prompting them to roll back to Windows 10. 

"In support of the Windows 11 hardware requirements, the minimum requirement for previewing Window 11 builds in our Windows Insider Program was set to match the overall requirements for Windows 11, with the exception for TPM 2.0 and CPU family/model – the yellow column in the chart below. These PCs will continue to receive Insider Preview builds normally depending on which channel they have opted their PC into."

See the following Windows 11 Insider Preview Build 22449 blog for more details:

https://blogs.windows.com/windows-insider/2021/09/02/announcing-windows-11-insider-preview-build-22449/