All ico buyers will get their coins once Lisk will be launched? Or people will get coins at some time, not all at once?
It's important, because if all people will get coins at the same time, they can easily flood the market and drive price below ico...
There will be a Lisk genesis block that creates all coins for all users at the same instant. As soon as the Lisk Foundation nodes go online and start propagating the Lisk blockchain using the genesis block as Block 1, anybody with the GUI wallet will instantly be able to access their coins starting on Block 2. Blocktime for Lisk is 10 seconds, so the plan is for everybody to have access to their coins within 10 seconds of blockchain launch.
I am pretty sure they will not launch the blockchain in secret.

Knowing Max, there will be a countdown clock.
Community nodes will start taking over from Foundation nodes after a week or so.
As always, I am not a Lisk insider, and I depend on Max to correct any mistakes I have said here.