I think there are 3 significant points to the extension
1) Being will now be required to retrofit the synthetic 3rd AOA and stick shaker inhibit switches to all MAX's. Shocking to me is the fact that Boeing pushed very hard for an unconditional extension. I have to ask what alternate reality does the Boeing C suite inhabit ? Instead of getting in front of the perception of a lack of safety culture at Boeing and be proactive they fought a logical safety upgrade to all MAX's only because it was going to cost some money. It took the politicians in Congress to tell them to do their job.....Really ?
2) The deadline for the retrofit is 3 years AFTER the Max 10 is certified which is now realistically early 2024 so that means passengers could be flying in a non updated MAX in the beginning of 2027. Can you imagine the Shyte storm for Boeing if one of the unmodified MAX's crashes and there was any nexus to the AOA ?
3) Both EASA and Transport Canada have not announced what they will require in order for an operator to register a Dash 7 or Dash 10 MAX in their jurisdiction. After being so badly burned by Boeing in the past it will be interesting to see if they are OK with the current time table.