Virginia – They claim that Democrats could pick up as many as three seats in a neutral draw. I have no doubt VA-10 could lean Democratic, although I doubt it’d be safe without a Democratic incumbent. Unless you significantly reduce the Black population in VA-3 and VA-4 I don’t see where Democrats get another one. They only won VA-4 by 16. Take enough Democrats from there and it becomes a competitive seat. Of course the reason that VA-4 exists is because the court told Republicans they needed to create a Black represented district. Breaking up these districts might give Democrats another one, or maybe two, but likely wouldn't elect any Black Democrats. I don't think the court will go for that.
Florida – Democrats already got their crack at the map when Republicans were told by the court to redraw the map this year so not to favor their party. Democrats picked up FL-7, 10, and 13 as a result, although they won FL-13 by only 4 points and they only won FL-7 because John Mica ran a bad race. This new draw gave Republicans FL-2 and FL-18. Even with a Democratic governor, Democrats can’t influence a draw that helps them win seats. Fair Districts Florida is drawn to prevent that. There are two South Florida Hispanic districts, FL-26 and 27, that could go Democratic if they can get Cubans to vote the same for congress as they do for the Presidency. That will have nothing to do with a different draw.
Democrats won only 11 of 27 seats and probably would have won 10 if John Mica ran a competent race. This highlights the biggest problem Democrats have, packing themselves together in small areas. Five of their districts are adjacent in South Florida, three are adjacent in Central Florida, and two are adjacent in Tampa-St. Pete.
Pennsylvania – A better draw would help the Democrats but not by that much. PA-6, 7, and 15 could be drawn as competitive seats but wouldn’t be certain pick-ups for the Democrats. Democrats lost these by 14, 19, and 20 this year, so a better draw wouldn’t have gotten them a win. PA-8 isn't gerrymandered, it's almost entirely Bucks county, and Democrats lost that open seat race by 9. It’s possible Democrats could pick up three seats but not without a wave. The Washington Post isn't talking about what's possible with a wave but in a regular year.
Michigan – I don’t see how Democrats could gain 2-3 seats with a better map. The state will lose a seat in 2020 and that seat is likely in the Detroit area where Democrats are strong. I don’t see a better draw for Democrats outside of Detroit winning them seats. Right now the map is 9-5 Republicans. Maybe they’d get 7-6 with a neutral draw. Maybe.
Ohio – I think Democrats would pick up a Canton-Akron seat in a neutral draw although the district would likely be one that Trump won. Outside of that I can see OH-1, a suburban Cleveland district, and a northern Ohio district becoming toss-ups. Democrats got very little of what they wanted in the 2011 redistricting but one concession they got was that the Dayton centered OH-10 was drawn into a district Barack Obama won in 2008. Republican congrssman Mike Turner won the district by 31 points this year. Democrats could potentially pick up 4 seats but it’d have to be a wave election.
Wisconsin – They say Democrats could gain two seats, but I don’t see where. I can see one seat moving closer to a toss-up but they aren’t going to get a draw in WI-1, 7, or 8 that’s going to turn 25 point losses into blue seats. Donald Trump won the Democratic held WI-3 by 4 points, even though Republicans attempted to pack the district with Democrats. So it's possible a neutral draw could actually cost Democrats a seat.
Illinois – This state was actually drawn by a Democratic trifecta. The redraw was a big success, since Democrats gained four seats and Republicans lost five. The state lost the fifth seat. Democrats lost IL-10 and 12 in 2014, before taking back IL-10 this year. A census seat loss could prevent serious Democratic losses but it’s not hard to see a couple of Suburban Democratic seats becoming toss-ups again.
Maryland – They don’t mention it but Republican governor Larry Hogan has a 71% approval rating. He seems a good bet for re-election. If that happens, as many as three districts that Democrats have could be toss-ups. That doesn’t mean Republicans will pick up any, but it should balance out toss-ups in some other states.
I know Democrats have been blaming redistricting for them not winning more seats but they got the courts to make new draws in North Carolina, Florida, and Virginia in 2016. Democrats only netted two seats in the three. I don't see the redistricting bonanza they imagine.