I dont know if it sooths your reservations at all the fact that all premined coins have been placed in escrow wallets, locked until 2020. You may check and confirm it at the announcement post.
The value of Sumo will have increased manyfold by 2020 also. Therefore, having the premined coins locked in escrow is not a valid nor a logical proof or indication of "sincerity". Furthermore, who has control of the escrow in the first place?
In any case where's the logic in dumping all premined coins in 2020 when at that time the number of coins in circulation will be enormous as well as the capitalisation, hopefully. By then devs will be "filthy" - no pun intented - rich, all they have to do is convert partial amounts into fiat. Dumping the whole premine as soon as the coins are released would be like liquidating their entire business and assets in corporate terms.
How's lump-sum instant wealth? No need for logic to figure that one out. With that kind of money, why would the players be concerned at that point in time about the circulation and market cap of a crypto that they just dumped on and made a killing as a result? No logic there.
Edit: In other words, after winning a record Mega Lottery prize, do you really honestly care about what happens to the Lottery Commission after that?