This is not for a fix from scratch. This is what they have been working on since the Lionair crash.
The question is whether it will satisfy the regulators (worldwide not just the FAA now) now that the second accident has happened.
And it's not just satisfying the regulators. Another "partner" in the decision to get the planes back in the air is the flying public at large, who were scrambling to avoid booking flights on the Max just before the grounding. That's why I'm skeptical that this is a fix that will be in place in 10 days. The flying public has to be convinced, and that will only happen if both crashes are shown to be from an identical cause that Boeing is addressing with the update. That's not going to happen in 10 days, I think, unless the investigation is moving at warp speed.
I know the point was made earlier in the thread somewhere, but it's worth repeating that this has some similarity to the EC225's demise in the offshore oil industry. Airbus never managed a good enough explanation and fix for what happened, and the North Sea oil workers refused to fly in them. It was the passengers that effectively killed off the aircraft model. Boeing and the regulators will have to do a better job of clearly explaining the problem, and why the "fix" solves it completely. At least in this case, the probable cause is known, again assuming both crashes were similar enough. If the root cause was different, the situation becomes vastly more difficult for Boeing.