Are you sure if the OnePlus One sequel starts at $550 16GB(?, could be 8 or 32) version? Cause that's what has been implied by OnePlus.
Yup. Based on my very positive experience with the OnePlus One, I'll be buying a OnePlus Two.
I buy all of my phones (typically used from Swappa) outright so even say $550 it will be less than comparably spec'd phones and realistically the OnePlus One was a better phone for me until the latest phones came out.
I sold my Nexus 5 and Note 3 after using the OnePlus One for about a week and tried the LG G3, Sony Z3 Compact and Moto X and preferred the OnePlus One and used it up until my Nexus 6 arrived.