Yes, in the current software world the only thing that is constant is change.
To me it seems like investing time in certain technologies or framework is similar to investing in stocks. ;-)
I remember the inital web applicastion days when servlets ruled and jsp was in it early days, we had decided not invest in jsp since it was not a proven technology. But later on JSP became huge( no doubt it had it own share of growing up to do - like model 1 and model 2 architecture).
Now we are working on a web application which was designed in early 2001 without struts. Now every once in a while I have a strong urge to redesign the whole application with struts, but just cant do it taking in to account the amount of efforts involved. So just have to live with the changing turf where sometimes you can move along with change or stay put with existing ones.
I believe the ability for a technology or framework to thrive depends on what value it offers, the ease in availabilty and use, who backs it in the commercial world.
Looking back java, servlets, jsp, struts was widely accepted.
while applets though appeared to be promising in browsers initally never lived up to its value proposition.
hmm it would be interesting to watch how JSF, AJAX moves along