Earlier today, Ed Boon tweeted out another mysterious image that appears to be part of his continuing countdown.
Based on Boon's previous countdown tweets, today's tweet should be about the number 15, but X is the roman numeral for 10. Some fans have replied hinting at the idea of some kind of crossover, like Street Fighter X Tekken. Boon replied to some of those tweets, humoring those who brought forward those ideas.
[Source: @Noobde]
Our Take
Boon's reply tweets to those suggesting a Mortal Kombat crossover fighting game make me think that it is out of the question. He likely would have ignored those tweets if they were actually on to something. That being said, however, a crossover with Killer Instinct doesn't seem out of the realm of possibility.