I can tell you the companies that we at Interface21 work with as a consultancy, some of which people would consider traditionally the larger, more conservative corporations, are excited about Spring, the value it providing them today, and the model it employes to sustain long into the future.
Spring's model is all about providing the best choice for generic technology infrastruture, capturing usage best-practices in a consistent manner that allows you and your development team to focus. That approach is never going to go out of style, regardless of the leading technologies of the day. Spring will continue to evolve, as the industry does, to continue to hedge bets on infrastructure, reduce risk, and abstract away complexity to provide a productive programming model for developers. Those armed with knowledge on how to leverage what Spring provides are always going to command the best rates in the market. Why? Because they'll be the ones solving real business problems.
We see on a daily basis evidence that Spring translates to measurable productivity and cost savings to businesses writing software in a wide range of industries, and we as a community need to keep pushing that message.
p.s don't forget the momentum -- look at the rush of Spring books. APress's Pro Spring sold out the first week it was released. Spring is still relatively new when you compare it to other technologies like EJB or Struts, for example, but it has momentum. And Spring is and will always be more than Spring. If someone asks you in a interview, "do you have EJB experience?" With Spring you can say definitely "YES", and not only that, but I know how to apply EJB better than anyone else when it is appropriate.
Lastly, as katetim pointed out, in the early days those leveraging a new technology/approach -- the many early adopters -- are often the best places to work.
Core Spring Development Team