This is a huge question on what to migrate and how.
If you just remove jboss esb from equation it would be quite simple migration path, which would still require some work but it is well known path that many have already done.
I would recommend you doing this:
JBoss 4.2.1 --> WildFly 10 (about to be released)
Seam 2.1.1 --> Seam 2.3.0.GA which does work with JSF 2
RichFaces 3.3.2.SR1 --> as you said migrate to latest richfaces 4.x
JBoss ESB --> difficult question, best to create new forum post over at SwitchYard forums, and ask how to do migration of just that.
JBoss Cache --> as you said Infinispan, which is part of WildFly
First migrate everything but ESB, then look how to migrate ESB as well.
Thanks very much Tomaz for quick reply, I'll post a question on SwitchYard forums
After doing some research it looks like Seam is no longer being developed and the latest version of RichFaces 4.5.x is no longer compatible with Seam.
"However since Seam is no longer being developed (and no part of RichFaces depends on it) we do not have to actively check if it is still working. If you find a problem then by all means file a JIRA issue, I can take a look at it and try to fix it but for us there is no requirement to maintain the compatibility."
Plus RichFaces will now "pursue a path of stability with our JSF approach, rather than a path of innovation".
I'm starting to think there's not much point upgrading to RichFaces 4.3 and Seam 2.3 it looks like a dead end.