Depends what kind of hotdeployment you refer to.
if updates to xhtml, html etc. kinda content then it should just work out of the box and changes should show up as soon as you refresh the browser.
if you are changing .class or .jar's then there has never been such support in any AS version (except for seam components which did a classloader hack to implement such)
In that case you have a few options in latest jboss tools release:
1) when you have done such changes right click on the module and click "Restart" and it will redeploy the module (without restarting the server)
2) if #1 is to cumbersome and you really want to restart the module on any .class file change then change the field in the server editor that currently says "\.jar$" to "\.jar$|\.class$" and it will also restart the module on every class change.
3) if #1 and #2 are too cumbersome consider using something like JRebel which is the only way to get something like "full hotdeployment" running on any java based system afaik.