The M2, or as it is called "funny money", had a single time event where people would be required to send the currency to each other, and on a random time (which has now passed), the GM / Zechariah rewarded people with M2 with the corresponding M (which again is tied to XMR for the time being). The future of M2 is something that only Zechariah knows - some say it's a dead currency, but every now and then a subtle hint of possible new use comes up. So unless you manage to squeeze info from rpietila himself, nobody can say for sure