You may have heard of it: Mobile.
The mobile user experience is fundamentally different from browsing the web on a desktop grade computer and a standard web browser.
Touch devices do not have a keyboard. You cannot control + click. You cannot right click. You cannot click and drag items. (Usually). Non-touch platforms have other challenges. Some do not support certain plugins.
This is going to require a reworking of the way we build websites.
Design and functionality will have to be layered onto content and structure based on the consuming platform.
The techniques to do this already exist. One is progressive enhancement, but at the moment this is more about adding advanced features for desktop-grade browsers.
It needs to go further than this. Websites have to work for everyone without discrimination. If they don't work, the user's experience of your site will be poor, or non-existent.
The reason I say 'new' accessibility wave is that we've already had to make websites for technology that interacts with pages differently from desktop web-browsers: screen readers.
Many ignored this old wave completely, deeming that market as irrelevant, insignificant or uneconomic.
I have bad news for you. That wave is being joined by a new one - tens of millions of people using non-traditional browsing technology, and growing every day.
If you've not thought about it, it is time to think about inclusive websites again. Websites will have to change to support not only screen readers, but mobile, TV and who knows what else.
If you didn't catch the first wave, you have a lot of catching up to do.