Put it this way, which I have said many times before. I knew and certain others knew the full confirmed roster back in Jan/feb and know now, there is no KP2. Who knows they may just drop it unexpectedly (highly doubt it), yet with normal development test cycles/QA submission and approval, these are done weeks/months in advance..
It's been out for 4/5 months now and is at version 1.08 + hot fixes included on top of that to a stage where they are comfortable with the way they want it to be. To add additional characters on top of that and then QA test, patch, etc,etc, is going to take more months and then, if they release another character, it's going to get patched again once it hits the end user like with all DLC due to possible time constraints and what not..
NRS will move on to their current projects fully using all available resources once they are satisfied with MKX, which they are now (based on their stream chat) and the next patch will be Quan's spell fixes and maybe more tweaks.