Nic Chan gave a presentation based on work done by @malvoz and herself, which reviewed eleven different Web map embeds from seven different Web map libraries, comparing them for accessibility success criteria from the Web Content Accessibility Guidelines 2.1. The results and presentation serve as an excellent resource for Web map developers who are interested in providing an accessible experience to their users.
The effort to standardize Web maps begins with identifying Use Cases and Requirements, and accessibility is a consideration for all. Accessibility of maps is a theme that should be incorporated in Web map standards, and this report may point to one of the core reasons that Web maps should be standardized.
Nic and Robert and the community would be very interested in any feedback that you might have about this topic and their work.