This is what is coming at block 90k.
In order to prepare for the next phase of Thuraya a new release gdbix 1.5.3 is available and it's activating protection against reply attacks & ddos attacks, it's a mandatory update before block 90k. And we are supporting Mac OS now 
This update is already released.
But what to expect at Block 90000?
yes the update is relesed and downloaded by wallet holders
but i think some of you don't know what is updated in the new version 1.5.3
the updated version work will start from block 90k
and update is for protection from DDOS attack
its a security update i belive