The next Terminator film will be Terminator Salvation. It won't feature Arnie, but will star Christain Bale as John Connor.
After the pathetic wet version we saw of Connor played by Nick Stahl in Rise of the Machines, hopefully this Connor will fall in line more like the character we saw in T2 and currently being developed in Sarah Connor Chronicles the TV show.
Perhaps like the Superman series, which now jumps from S2 to Superman Returns avoiding any connection with S3 and S4, T4 will follow on from the TV series, and Bale will get he chance to be the Connor we know he can be.