Anyone who played it smart has already recovered their investment and thus taken some profits out of whale pockets... and anyone else can still start playing for free just to get faucet-site-like payouts. I'd even argue that paying for level 1 drug-production upgrades will still recover the investment in about a week.
But... I fully agree that the game will not be sustainable unless some groundbreaking new features are invented. I say invented because nothing in the original mafia-wars-like structure allows for a sustainable economy nor compelling gameplay...
The biggest flaw of this game... if you really think of it as a cash-cow... don't sign up and buy upgrades... just reactivate 1000 dead alt-accounts and reap the benefits... I wonder how many of those proclaimed 5000 players are actually real ;)