A little optimistic, I feel.
I don't know if 2006 will be the "year" of OPML. But I'm certainly betting on OPML to trounce OML, XOXO etc. And to drive a great many new applications.
A couple of reasons :
First. I downloaded and looked at Taskable (http://www.taskable.com/). I haven't found a use for it myself, but it is kind of intriguing.
Like RSS it "bends" internet space in a new way. When I started to see what was going on with blogs and syndication I called it the "flow internet" : a sort of alternative web, based on fixed people and mobile information. (Rather than fixed information and mobile "surfers")
It just kind of felt different.
This Taskable thing is the same. The information feels like it has a new "shape".
And it's a different shape from syndication. That's why I don't think RSS will simply expand to include the same applications.
Of course, the tree vs. list thing is part of it. But it's also which bits are dynamic and which bits fixed. Unlike an RSS feed, the data is not, itself, sequenced in time. It's permanent. But it can change over time, as the host updates it.
Secondly, part of Winer's genius is that he can recognise useful (if mundane) applications for his stuff; unlike his opponents who normally start with an aesthetic point to make : "want to do outlines in XML? here's how to do it properly".
Dave's OPML strategy, in contrast, is a sequence of little applications. First OPML as native format for Radio Userland. Then as a format for keeping your blogroll. And your subscription feeds. (If you were using Radio) Then as a directory of favourite music. Then, later, as a directory of podcasts.
Then, as the native format for OPML-the-editor. And in the process, becoming part of the organizing principle behind Scripting News.
In each case, people have been working with the format, getting used to it. I don't see XOXO woven into people's applications the same way.
The recent TechCrunch story was the real bombshell. Suddenly Dave's putting a subscribed-to outline, publicly on his site for everyone to see. It inspires a frenzy of activity as blog software and aggregator authors rush to support this.
Until then, OPML was largely private. Something you used for your notes, or to produce HTML. Now it's become a public language for communicating and people are going to be looking for new applications.