Terminator Salvation was not much praised by the hard-core Terminator fans, but the film did pretty well worldwide. And movie sequel is definitely planned. Director McG has been talking to IGN about Terminator 5:
Mcg is taming down the potential plot (that was about an all-out attack/invasion of Future Skynet into our time) he previously revealed for Terminator 5. Now it sounds like John Connor would come back to our time with ‘only’ a nasty Terminator to chase him (yep like in ‘good old time’).
Well, he should stick to the invasion plot rather than planing one more useless chase movie.