We are not dropping the old deployer framework.
It just won't be able to take advantage of some of the features of the new framework,
when it is eventually written.
Using something like SimpleSubDeployerSupport frees you of the most of the
dependency on the deployment framework.
e.g. I recently wrote the new Bean Deployer using SimpleSubDeployerSupport
The SimpleSubDeployerSupport will continue to be supported as its used by 4.0.x implementations. If you want more assurance create a unit test that illustrates you deployers usage and submit it to jira as a patch so that it can be integrated into the testsuite.
The 5.0 codebase is potentially a different story.
Thanks for good and quick replies!