Both variants, with or without the comma, mean exactly what Rand intended them too: That the four nights in Sydney ARE FOLLOWING -- i.e, _A_F_T_E_R_ -- some other nights elsewhere.
THe only way to change that into its opposite is, not by inserting or removing commas, but changing "following" to *its* opposite: "Four nights in Sydney[,] *follwed by* some other nights elsewhere".
HTH!