"StarCraft II" will finally have an updated 1v1 different race ladder that will cater to players who wish to use another race without having the level of their primary chosen race be affected, as reported in the StarCraft website.
This "Starcraft II" update was thoroughly discussed in the aforementioned site and will be known as Patch 3.7. Besides not having any impact with the ranking of your main race; the latest add-on from Blizzard Entertainment will also not diminish a player's MMR.
Such an update has long been clamored by the "StarCraft II" community via constant feedbacks and thus will create such an enthusiastic response from players as a huge amount of the demographic want to access other races without having their said main character be upset in the ranking ladder.
"Starcraft II" players upon entry in the game after the application of Patch 3.7 will be presented with a different season. This will then require you to engage in placement matches prior to your procurement of a race of your choice. Be warned however, that it will take you five (5) matches even if that said race has already been ranked prior to Patch 3.7.
This is the "StarCraft II" developer's assurance that everyone will be on the same playing field with the updated patch.
After the completion, a ranking race option will be given to you which will include the chance for a prior "Random" race option to possess a ranking of its own.
Issues on MMR placement have also been taken into a great deal of consideration. Blizzard Entertainment opted in having the MMR of an off-race be at the same level as the MMR of one's main race along with a high "uncertainty" level.
This logic will allow the standards to move at a certain pace during the opening salvo of the Starcraft games.
For more questions to be answered on "Starcraft II" Patch 3.7, you can visit the Blizzard website as linked above.