No. No abbreviation can be locked in to only defining one thing. Language is largely abstract, and the same abbreviation can have and often does have different meanings depending on the context. So long as the context is established, you can use whichever abbreviation you like. If you make a post about titanfall 2 and then use TF2, it is established that you are not talking about team fortress 2 and therefore is correct. Same with the vice versa. The only time that titanfall should not receive the abbrieviation TF2 is when both games are being discussed in the same context. In this situation, the op should define which context is for each one, so not to confuse he audience (ex: writing "team fortress 2 (TF2) is fun, but so is titanfall 2(TTF2). By doing this, there is no room for confusion, and you can establish the use of whatever abbreviation you'd like.