I think there will always be a Terminator reboot in the near future.
The sad thing is that T4 could have been interesting [if not great] if it had gone the way it was originally written.
I've been re-watching the Sarah Connor Chronicles which has put me back in a Terminator mood but it's had to get excited for another film at this point.
I wonder where we'd be if Jim Cameron had gone with the 'happy' ending to T2 instead..