deployment desriptors are specific to app servers
Ok this is misleading, some app servers *support* server-specific descriptors, like jboss-web.xml, but no deployment descriptors (web.xml) are not application serve sepecific. But this is the good news, just keep all the descriptors in your WEB-INF dir, and deploy them. The app server that needs them will use them, and the other app server will ignore it. For example, Oracle will ignore your jboss-service.xml file, so no problem.
so I wanted to know when Myeclipse can support deployment of application to diff servers
Yes, all of them to be more specific, please read how here: http://myeclipseide.com/enterpriseworkbench/help/index.jsp?topic=/com.genuitec.myeclipse.doc/html/quickstarts/appservers/index.html
can myeclipse even generate the deployment descriptrs as well.
No, these are not files that can easily be generating because their layout/contents depends entirely on how you want your application to run.