The best replacement for 4x5 is 8x10.

The best alternatives to 4x5 are rated as following:
★★★★★  8x10
★★★★  5x7
★★★  6x7
★★  4x6
★★  6x6
★★  6x9
★★  medium format
★  iq180
  hasselblad
  120
  mamiya 7
  2x3

Your alternative for 4x5 is not listed? Suggest!
Speaking about 4x5, one probably shouldn't forget about roll film.

Other search terms related to 4x5 and their ratings are:
★★★★★ roll film
You have in mind a companion for 4x5 and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of 4x5 in all years. Click on graph for more.
4x5
8x10
5x7