Will the discontinuation of the standard voices in Microsoft affect Pilot2ATC? 

Per this article by Microsoft:  Upgrade to Text-to-Speech Neural Voice  by 31 August 2024 | Azure updates | Microsoft Azure

I assume it will but I'm not sure if these are the same voices I select in my settings, etc. 

In my opinion, text-to-speech (output) should work in the near future but won't be supported any more.
Speech recognition (input) is deprecated, so it may be removed in a future release.
Both shouldn't affect Windows 10 22H2 as it's the last release for Windows 10.
But only my thoughts - no one knows if a future fix may not make it stop working.

 

Extracted from your link:

Text-to-Speech currently supports both standard and neural voices. However, since the neural voices provide more natural sounding speech output, and thus, a better end-user experience, we are retiring the standard voices on 31st August 2024 and they will no longer be supported after that date.  

 

Regarding the opposite - speech recognition:

https://learn.microsoft.com/en-us/windows/whats-new/deprecated-features

Windows speech recognition

Windows speech recognition is deprecated and is no longer being developed. This feature is being replaced with voice access. Voice access is available for Windows 11, version 22H2, or later devices. Currently, voice access supports five English locales: English - US, English - UK, English - India, English - New Zealand, English - Canada, and English - Australia. For more information, see Setup voice access.

 

A link leads to https://learn.microsoft.com/en-us/windows/whats-new/feature-lifecycle

Terminology

The following terms can be used to describe the status that might be assigned to a feature during its lifecycle:

• Deprecation: The stage of the product lifecycle when a feature or functionality is no longer in active development and may be removed in future releases of a product or online service.
• End of support: The stage of the product lifecycle when support and servicing are no longer available for a product.
• Retirement: The stage of the product lifecycle when a service is shut down so that it's no longer available for use.
• Remove or retire a feature: The stage of the product lifecycle when a feature or functionality is taken out of a service after it has been marked as deprecated. The feature is removed from newer versions of Windows, but still exists in older versions and is supported until those versions reach end of support stage.
• Replace a feature: The stage of the product lifecycle when a feature or functionality in a service is replaced with a different feature or functionality.