I would guess whenever the store your trying to buy from gets more stock?
This isnt the wrong place to ask, its just kinda the wrong question to ask.
A better question would be to ask if anyone knows who has one in stock, and i would say check eBay seller MitxPC or try their website directly. Im pretty sure as of last week they had plenty of both M1 and M2.
Why do you not want the M2 out of curiosity? Your getting an awful lot more power out of it for only a few dollars more.