There has been talk of Kyle Reese being a sequel. Justin Lin wanted to do an alternative dimension movie in which Kyle Reese and Sarah Connor would be back in the next Terminator movie. As a website we have also discussed how he could return in a smartly executed Cameo… with a science fiction series like Terminator the ability to possibly utilize time travel provides endless possibilities for future plot lines. It just depends on how they use them.
There was also talk of Justin Lin wanting Paul Walker to take over the role of Kyle Reese this was something met with fan hate. There is only one Kyle Reese (Michael Biehn).
Check out the following articles here:
How to bring Kyle Reese back (Cameo or full starring/ both) – Optional
Paul Walker to play Kyle Reese?