new iMac software version for a 2015 iMac

No, the 2015 iMac (I have one) can go to Monterey, which is three versions of the MacOS behind Sequoia. Also for the AI features, only the more recent Silicon Macs can use that with Sequoia. For instance, I have a 2019 Macbook Pro that can install Sequoia but it is too old for the new AI features.

I believe that our 2015 iMacs are considered "obsolete" by Apple which means they no longer support them nor stock parts, etc.

You can only upgrade a Mid 2015 iMac as far as Big Sur.

The person who said that they have a 2015 iMac running Monterey must have a Late 2015 model. You can update the Late 2015 iMacs to Monterey, but no further.

Apple Intelligence is only available on Macs that have Apple Silicon processors. Your Mac uses an Intel processor. The M-series Apple Silicon processors have special hardware to accelerate "AI"-related computations. Apple calls this hardware the Neural Engine. Intel is now putting special "AI" hardware into their processor chips, but the Intel processor in your Mac is too old to have this special hardware – either Apple's version or Intel's version.

Inder preet wrote:

Hi can my iMac mid 2015 late the latest version of the apple software with AI

No, it is far too old. A mid-2015 iMac can't be upgraded beyond macOS 11 Big Sur. Neither can a late-2015 iMac, which is limited to macOS 12 Monterey.

Servant of Cats wrote:

You can only upgrade a Mid 2015 iMac as far as Big Sur.

The person who said that they have a 2015 iMac running Monterey must have a Late 2015 model. You can update the Late 2015 iMacs to Monterey, but no further.

Apple Intelligence is only available on Macs that have Apple Silicon processors. Your Mac uses an Intel processor. The M-series Apple Silicon processors have special hardware to accelerate "AI"-related computations. Apple calls this hardware the Neural Engine. Intel is now putting special "AI" hardware into their processor chips, but the Intel processor in your Mac is too old to have this special hardware – either Apple's version or Intel's version.

That is correct, my 2015 iMac is the late 2015 model which is on Monterey, but the mid-2015 iMac is limited to Big Sur (one version older), as noted by the other two who responded. I mistakenly assumed a late 2015 model when in fact the original poster did indicate they had a mid-2015 model.