...critical question is: will they stay and register to vote?

They're American citizens just like any other

...generalized terrorism. The same tactics used on all POC since Jim Crow days. It's going to be an uphill battle for Dems in Florida.

Seems unlikely, but I suppose it's possible

CBS NEWS
December 5, 2017, 7:48 AM

In the three months since Hurricane Maria, hundreds of thousands of people living in Puerto Rico left for the U.S. mainland. More than 215,000 arrived in Florida since October 3, when the state began counting. One study estimates more than 470,000 people will leave Puerto Rico over two years ...

https://www.cbsnews.com/news/puerto-ricans-relocate-to-florida-face-difficult-transition/

Could tip the scales locally and nationally.

And a total of over 400,000 are expected to migrate to the US in the next 4 years.

So, your number looks pretty accurate. I would include a link but I can't on this tablet. Well I could if I wanted to spend half an hour doing it.

I see Struggle has a link upstream.

South Florida is more crowded. Most are staying with family who are already here. I think a lot of them don't know themselves if they are going to stay.

The economy was terrible in Puerto Rico before the hurricane, now it must be impossible to find a job.