Source: Kronos FAQWill there be Character Transfers from other Servers?Characters Transfers from other Servers will never be possible.
Ares -> Kronos is not possible because Ares is.. 12x ? rate server while Kronos is 1x. However, it was stated many times that when Kronos reaches its end, there is possibility of creating its TBC version to allow players to continue (as it was done with twinstar WotLK -> cata, characters were copyed and those who wanted to continue on cata were alowed to do it while others were alowed to stay on wotlk).
This all depends on how much Kronos succeeds.