If Jobs never left Apple would have gone down the drain.
Unknown_K, I disagree.
Sculley didn't trust Jobs, but the very things that have made him and Apple a success today were there then. Sculley made an even bigger mistake by putting Jean-Louis Gassée, a guy with an ego equal to Jobs, but none of the experience. He was a sales and marketing guy. And he was greedy. If anybody nearly killed Apple it was he and Sculley.
The single most important thing that Jobs brought to Apple was change and a forward looking philosophy. By 1985 with the introduction of the Laser Printer, the Mac's position in the market was solidified and would be unparalleled until Windows 3.1 stepped forward in the early 90s. Apple had over 8 years from which to capitalize on the market with huge profits while developing the next generation. But Gassee didn't have that vision and caused Apple to become a dinosaur, instead of an innovator by the time Microsoft became a real threat.
As soon as the Mac was out the door in 1984, Jobs began pushing for a Unix based system to control it all (Big Mac- which Gassee hated), going so far as Apple buying a $1 million license from ATT. He was also pushing for miniaturization, bringing in PowerBook-like prototypes to board meetings, something Apple resisted because there wasn't enough profit in it, and cost too much to develop.
So think about it, Jobs was preparing for the future, had he stayed at Apple, the Mac would have replaced the Apple II anyway as the cash earner if only in education, consumer and publishing industry. But more importantly, he would have migrated the Mac OS experience to a UNIX platform over a decade before OS X and blown Windows 3.1 out of the water in 1992, instead of a disappointing and buggy upgraded vis-a-vis System 7. Also, he would have pushed for the miniature laptop and probably bypassed the Luggable completely, blowing away the industry with the PowerBook much earlier.
No if Jobs had stayed, Apple would have made less profit, but as Jobs has repeatedly shown, that has ultimately been less important than its progressive innovation. Even after Jobs return he churned out his own Apple IIIs and Lisas (the Cube anybody?), but like those dinosaurs, the technology created was readily subsidized into products that blew away the industry. I've no doubt that had Jobs stayed, Apple would have done just fine and possibly be in a better position that it is today.