Bullish language, given that some company has launched a service which only runs on the latest version of Opera - maybe "mainstream" actually means "a few hundred members of the mobile blogger elite".
The use of "had" in the original article's title almost inspired me to write about it - I for one don't believe maybe a few hundred potential users counts as mainstream - but with Carnival doing its usual to amplify the speculative into the done deal, I feel again I have to point out that they are doing a disservice to their readers.
One man's "perrenial thought leader" is another man's unrealistic dreamer. Predicting the future can be a very valuable exercise and can help drive the world forward; it's a useful exercise, but you have to avoid hubris and only declare yourself proven right in the mainstream when you actually are proven right in the mainstream, not just when someone launches the first service onto the market which approximates your ideas.
As predicting the future goes, mobile AJAX is about as obvious as you can get - after all AJAX is pretty simple stuff, a few basic browser extensions wrappedn up in some Web 2.0 wank goodness. When mobile data becomes really really really cheap and really really fast, and mobile phones have lots and lots of processing power, it will fill a valuable niche in the mobile services value chain. That's it though. It won't solve device fragmentation, it won't be magically easier to use ro faster or better than many other ways of providing mobile content, and at current speeds and prices it will have to work very very hard to prove its worth.