Chris,
Yes. You can open .PC6 files with TL7. File->Open (Local Drive). Just change the "Files of Type:" box to "All Files".
I have ported code from the old M series PLCs as well as my modern FMD and Nano-10 programs to work with TL7. Everything has compiled and the code seems to run as expected on the new hardware.
The things that you need to look out for are the specialized I/Os and COMM port #s. You should, also, look at your DM usage and the non-volatile memory usage. It's not a TL6 vs TL7 issue, it is simply that this stuffs moves around from PLC to PLC.
Gary D