1) Maybe.
2) I do see this, given the money poured into this cycle, as a potential possibility. It may not just be LLM's. To another comment you are betting against the whole capitalist systems, human ingenuity and billions/trillions? of dollars targeted at making SWE's redundant.
3) I think it can disrupt only knowledge jobs, and be some large time before it disrupts physical jobs. For SWE's this is the worst outcome - it means you are on your own w.r.t adjusting for the changes coming. Its only "world changing" as you put it to economic systems if it disrupts everyone at once. I don't think it will happen that way.
More to the point software engineers will automate themselves out before other jobs for only one reason - they understand AI better than other jobs (even if objectively it is harder to automate) and they tend not to protect the knowledge required to do so. They have the domain knowledge to know what to automate/make redundant.
The people that have the power to resist/slow down disruption (i.e. hide knowledge) will gain more pricing power, and therefore be able to earn more capital taking advantage of the efficiency gains made by jobs being redundant from AI. The last to be disrupted has the most opportunity to gain ownership of assets and capital from their economic profits preserved. The inefficient will win out of this - capital rewards scarcity/people that can remain in demand despite being inefficient relatively. Competition is for losers - its IMV the biggest flaw of the system. As a result people will see what has happened to SWE's and make sure their industry "has time" to adapt particularly since many knowledge professions are really "industry unions/licensed clubs" who have the advantage of keeping their domain knowledge harder to access.
To explain it further even if software is more complicated; there is just so much more capital it seems trying to disrupt it than other industries. Given IMV software demand is relatively inelastic to price due to scaling profits, making it cheaper to produce won't really benefit society all that much w.r.t more output (i.e. what was good economically to build would of been built anyway in an inelastic demand/scaling commodity). Generally more supply/less cost of a good has more absolute societal benefits when there is unmet and/or elastic demand. Instead costs of SWE's will go down and the benefit will be distributed to the jobs/people remaining (managers, CEO's, etc) - the people that dev's think "are inefficient" in my experience. When it is about inelastic demand its more re-distributive; the customer benefits and the supplier (in this case SWE's) lose.
I don't like saying this; but we gave AI all the advantage. No licensing requirements, open source software for training, etc.