Reported by Korean gaming site Game Focus, Titanfall Online was in development for around three years. They held a limited time player test, though reception was mild at best. Lack of interest wasn't what drove the decision to cancel, but the changing nature of online games.
A Nexon representative had this to say:
It is true that Nexon and EA have agreed to cancel Titanfall Online under a business decision. After much deliberation, it was decided that reallocating development resources to another project was better for the company.
Being marketed for Asia, the western hemisphere heard virtually nothing about the game. Our sympathies to those who looked forward to the game's release, all the same.