think it wouldve been a good idea for facebook to welcome bitcoin and Mark making a big turnaround for technology. Im pretty sure Mark is quite skeptical about bitcoin because of its volatility. When he invested his time and effort in facebook, he knew from the start it will make big in the future.
Facebook is taking a serious look at blockchain technology and cryptocurrency when Facebook officially has Blockchain CEO in their new staff. This proves the seriousness of Facebook and I think Facebook's ability to release his coin is very likely to happen.