Has XML Peaked?

Personally, I think it's a mute question really. Optimization and interoperability are the key elements to any of these technologies regardless.

They've all been around for years and will be around in different evolving guises for many more. I remember my first introduction to "similar" tech 30 years ago and most of that's the same today!

My 2 cents.

I really don't believe so. At the end of the day, it's clunky and can be expensive to process but CPUs are getting faster and available memory is still increasing. I have been told many times there are alternatives but I have yet to find something that can be parsed to get 'meaining' as easily on a mainframe as it can on a PC whether you are using Java, C++ or assembler ! JSON gives us a hint in the name....it's geared towards JAVA IMHO and as such is only appropriate when using Java which is simply not appropriate for all development scenarios.

XML is at the foundation of many, if not most, integration efforts, Web services, and SOA projects. We finally have something that’s bringing together all the world’s systems and data. There will be a lot of XML around for a long time to come.

Well, in fact JSON is language independent and is based on the ECMA Standards – that apart I guess one way to put it in perspective would be drawing a parallel with Java and PHP. If you want something up and running quickly then PHP is a great way to go whereas if you want something sustainable, reusable at the enterprise level then you go for Java or Microsoft based technologies.
Both, XML as well as JSON will co-existence but the usage will depend on the intent – Long term or Short term!

Is SOA dead? surely it is not. It is now mainstream. The same thing is true about XML: it is not fading. It is De-facto standard for many years to go.
The trade of of XML Platform independence for its less than optimal resources consumption is reasonable.

Lets face it, XML is here for the long term. In essence its nothing that new at all, and as an early post stated, many "technologies" can find their roots some 30+ years ago. XML facilitates integration and SOA, unless there is something really revolutionary round the corner regarding computing, then I dont see these 2 dissapearing for a very very long time...

Also XML is now being used as a starting point for other technologies, just look at WPF and Silverlight XAML, its basically XML with some add ons, and there is nothing wrong with that....

Different problems lend themselves to different technologies. JSON came about because AJAX developers found that working with XML in JavaScript--the X in AJAX--was a lot of work. JSON cleverly used functionality in the language to effectively bind wire protocol automagically to objects. Problem solved. JSON turned out to be a nice succinct notation that then found application elsewhere, where the bloat of XML wasn't needed.

But there will always be problems that require the richness of XML ("richness" is just bloat viewed from the other side). Schema validation, transform, linking--these are incredibly valuable capabilities and have an essential role to play in many sophisticated applications.

XML isn't going anywhere, but it will need share the stage with alternatives like JSON. This is identical to the REST vs SOAP debate. Smart developers eschew religion and ask themselves what problem they are solving. The answer usually suggests the most appropriate technology.