For the new install, SME6 is way to go, but for the upgrade from SME5.6, if everything works and settled on SME5.6 already, maybe its not that much advantage.
For myself, I've upgraded (via fresh install)my 5.6 home server (nothing important) to SME6.beta, and now upgraded it to 6.0 final, but for dozens production servers already running SME5.6 I am not pushing upgrades.
If some of them need to be reinstalled one day, then (maybe) I will upgrade at that time. It was the same dilema about upgrade from 5.1.2 to 5.5 and on most servers I've skipped it until version 5.6 proved to be worth upgrading to.
"death of SME" may be birth of new and improved version of server with many options not offered by "officialy unsupported" Mitel's releases. Where is good chance of make this distro much better and worth upgrade to every new release in the near future, you may help to make it happend as well.

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