Right now if Tony dies the project is over and out, so witnesses can still be centralised in Tony, as the project is still fully dependent on him anyway. Over time though it is indeed important that more people take on leadership roles so that the project can go on without him if necessary, and indeed witnesses become more decentralised as well.
True.
The cashback witness MEJ...
http://www.cashback-witness.com has already been adopted by many people (see:
https://byteball.fr/stats.php) but will never be a full replacment of Tony original JED....
True decentralization will come only when independant witnesses will be added in the default list by Tony. There is not sufficient attention/motivation from end users to the witnesses to make them change their default wallet parameters (actualy they just don't care...). Or in other words: thoses who are concerned will never be the majority.