The 7 Series FPGA Transceivers have the capability to support Tx and Rx running at different line rates. More details on the different PLLs (Channel PLL and Quad PLL) and divider values in the 7 Series can be obtained from the "Shared Features" chapter of the
7 Series FPGAs GTX Transceivers User Guide (UG476).
However, version v1.3 of the 7 Series FPGAs Transceivers Wizard released with ISE 13.1 software does not let you select independent line rates for Tx and Rx. This is a known issue and is addressed in the next version of the wizard released with ISE 13.2 software.