there is no fork, just a new wallet...you can leave your coins wherever you want...although generally it's not a good idea to leave anything on an exchange unless you are actively daytrading...you risk not being able to withdraw when you want due to wallet/system downtime, or at worst being victim to hackers or exchanges closing down for whatever reason (exit scams, government regulations, etc)...not to mention having no control over the private keys (eg in the case of a fork or airdrop)

also, i dont believe Cryptopia will stake your coins, so you are losing out on that passive gain when leaving coins there