If Adobe AIR and Microsoft Silverlight continue to gain traction then they could begin to replace AJAX-style implementations for feature-rich web sites.
The key word here is could.
The key word here is could.
To use Silverlight as an example, I think it sucks. It's bloated and I don't get it. I'm tired of playing catch up with MS technologies and all the freaking featues they pack into them. I mean: ASP.NET. ASP.NET AJAX VB.NET 3.0, LINQ, F#, C#, J# (being retired), VBScript, VS 2003, VS 2005, VS Team Foundation, Windows Workflow, Windows Communication Foundation and Windows Presentation Foundation. Seriously?
Windows Workflow in particular is extraordinarily huge. If keeping a program in one's head is important (and it is), then it's not going to happen with Windows Workflow. As I get more comfortable knowing what I want to code and how I want to code it, I'm finding myself just wanting to use stuff that gets it done in the path that is the most natural to me.
Silverlight? No, thanks.
I agree that keeping up with the many languages is difficult. But it's necessary if you want to be the best and on top of the game. Test drive a lot of different languages and pick the one that meets your needs and feels most comfortable. Sometimes driving more then one language is the best option.
We could argue until we are all blue in the face about what the best language is and what the next "big one" will be. I wouldn't focus as much on the language in 10 years, no one is looking to utilize that today. The future is important (as many get rich making it) but keep in mind a lot of companies that have been ahead of there time got bit in the ass from it.
They must realize that the only way they will gain acceptance amongst hackers is to convince them that Silverlight is not a traditional MSFT product. A few months ago they were kissing ass to Arrington and a few others trying leave positive impressions about the platform and convince everyone of its openness.
But they may already be in trouble because AIR seems to have an edge in early adoption so far. Pownce is written in AIR for example.
It'll be interesting to see how things play out. There is a huge need for certain features of Silverlight and AIR (like local file system access and a network API), but I dont know if those will be compelling enough to drive either of these to "critical mass".