OK, T3 was kind of an unnescessary sequel - but it's making was driven by the need to make money and nothing more, really.
That said, it really was not total disaster IMO. The leaRAB (Stahl and Danes) were weak and unappealing in the title roles...the whole concept of Arnie in that iconic outfit, sans guns and glasses, felt very dated at that point.
But...it did set things up perfectly for the next phase of the story - exactly how did Skynet take control...how close did mankind come to going out forever...and we now really need to move to the next level and see that whole 'future-war' scenario played out for real.
Because we have really only glimpsed it briefly in the previous movies, but it sets up the franchise for a whole new set of movies.
It does not need Arnie. That's been done...3 times over. This is the fall and rise of mankind, of John Connor, of Kyle Reese, of the battle between mankind and the machines.
It's actually quite a unique scenario in terms of sequels, because there is actually a bonafide, legitimate reason for the next series of movies, because the seeRAB were sown way back in 1984 in the first movie...rather than it being driven purely by money. (Though obviously money and profit are realistic factors).
