I hear people saying that the playerbase is too small to make pre vs pre matches not be inconvenient for premade teams, so the question why are bothering with premades to begin with? Here’s the plan guys we need more people to start this game to up playerbase so lets promote it to him like this:
"Hey guys and gals come play this fun new game were the first mode(s) you can get in to being a fresh new solo queuing player is going to now be populated with 5 man preorganized teams that will simply steamroll you from every angle why the rest of your team is milling around trying to work together. Doesn’t that sound great?!.. Hey wait where are you going ? Come back! It will be fun to get team crushed before you even can think about Ranked later on ( hell even getting to level 7 for that matter ) . Come on, give it chance it is fun really… " 
Look from the look of the set up right now of the game it looks like this imo:
You start out fresh with no merc or map knowledge you get a free merc ( Skyhammer ) and 3 other random mercs of the right combo of roles to be able to choose from for all aspects of the early game. You play learning the characters you can play and the mercs to look out for from encounters with them. Alone the course of playing you meet and maybe talk in game with your team ( gasp ) and get to like some of the other players and decide after you played awhile ( to level 7 ) to invite 4 of those game friends to play with you to try for a rank and some cool skins this season.
With the new premade system allowed coming in soon the playerbase is now possibly going to be separated even further by making static groups that will always play together in Quick Match and likely use their own voice chat and ignore the ingame one ( now there will even less strategy going on in voice than now ) leaving now 2-3 player out of the loop and possibly repeatedly separated from the now “team” effort ( removing the rest of the team ) and getting picked off being out of position .
Bottomline/ TL:DR : This new premade system is going to possible do more to separate the playerbase than making them wait a bit longer in queue for another premade dominated group. But, if this system is so wanted by the current playerbase then there should be no problem getting a quick queue for a premade vs premade match because everyone will be doing it!