will there be automatic replacement of the old coin with the new coin in yobit 
No you have to sell the old coin and buy the new coin. SWTC is not TOKEN See this from a post on the first page in this discussion " Please understand that TOKEN on Yobit is not SWTC.. the Dev of TOKEN on Yobit is
TillKoeln see his post about the future of TOKEN here.. https://bitcointalk.org/index.php?topic=1527955.msg15374073#msg15374073
He is also the Dev of the coin NANOX currently being traded on Yobit and is active on the Yobit chatbox
check this.. https://bitcointalk.org/index.php?topic=2103771.0
SWTC is in no way connected to him and he is not the DEv of this coin. Team of Devs for SWTC will be announced in a few days time after being democratically chosen based on interest to volunteer to be part of the team that will be developing and managing this coin."
Do your research take a wise decision and stick to it.. Dont worry about what other people say or think!