Almost all of these what-if questions answer themselves. If Order 66 failed, then Order 66 failed. The Jedi aren't killed. Palpatine says exactly what he thinks (or at least wants Anakin to think) would happen in that case: "If they are not all destroyed, it will be civil war without end."
Responsible speculation sets more specific terms, or else these questions are asked just for engagement rather than an actual search for a good answer.
