From what I've heard the SData technology is still being developed. That's only 1/2 of the new technology. Getting the order entry screen to work via HTML/CSS/whatever in any web browser was the challenge. That's a complicated screen - lots of popups, panels, etc. And they decided that they couldn't get it to work good enough for them to release it as an option.
The next SData feeds with the backend Tomcat engine allows for other UIs to be written to communicate with Accpac - those could be written in VB (joking), VB.NEt, C#, Delphi, iPad, Android, etc. That would allow them to modernize the interfaces.
The exciting part about the web interfaces is that they were going to be modifiable so that those of us customizing screen mods could integrate the customizations in a much cleaner way. There's nothing stopping Sage from using a different development environment to allow the same thing.