The GSM (a1901) version will have the Intel modem like last year and the CDMA (a1865) version looks like it will have the Qualcomm modem compatible with all carriers, including GSM. Really a bummer, Intel doesn’t make a chipset that will support band 71 for T-Mobile and it doesn’t look like Apple included support for that band in the Qualcomm modem.
As far as unlocking goes, each carrier has their own set of requirements that must be met before they will unlock the phone except for Verizon.