Are you talking Struts 1 or 2?
Struts 1 is still
very widely used.
I went to a conference last year and attended a talk
comparing web frameworks. The speaker asked what framework everyone was using (you could vote more than once) and Struts 1 users outnumbered every other framework by a very large margin (probably every other framework
combined). It's got problems, for certain, but it's got a huge installed base and user community and isn't going away any time soon.
As for what's next,
this article has some interesting analysis.
In my opinion it just takes a few days of tutorials and reading to get up to speed on a framework. I wouldn't invest in a class.