They've been working on this for years. They weren't prepared in 2017; they never expected to have this much power. This time they knew what they were getting, and had all the ducks lined up in a row.
"they" will lose their majority far sooner than that. Everyone up for election in the midterm (the entire house) is going to be worried that if they don't defect not they will be voted out. Of course they are balancing that against those who vote against them for defecting. Still I expect to see defections happen in a couple months.
I don't expect to see very many defections. This is what the voters asked for. I don't see the voters changing their minds.
Nor do I see any of them developing a conscience. If they do, there is a very good chance that they will lose a primary challenge.
The legislature may change hands just because it's closely balanced and things do tend to swing a bit. It's not so much about voters switching, as about small amounts of turnout making a big difference.
So as far as I can tell, expect to see more of exactly what we were told was going to happen.
I don't think we'll see defections per se, but we will see some "retiring to spend more time with the family" or "looking for new opportunities in the private sector."
the incumbant has a big advantage and so it isn't hard to beat that. Besides the reason they will defect is fear of loss - those who defect are likely aware that they won't get reelected if they don't. They might lose a primary but if whoever wins support trump they are unlikely to win. That is the whole point of defecting - if you don't you lose for sure.
That's healthcare for 85M people and half the births in the country.