No, the size will change, but the percantages will not.
They most assuredly would change. Back to my hometown. Under the current system, San Francisco gets one Rep who's always a Democrat. If we got 7 reps, we'd probably send 2 Greens, 4 Democrats and 1 Republican or Libertarian. That's a Democrat-to-Green ratio of two to one. As it stands now, the ratio is one to sombrero.
Sure a lot of new seats would be sucked up by the Republicrats, but a lot of them wouldn't, and that's a step forward in my book.