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?
Well that's a fact but if you believe that in 3 years the price of Sumo will have increased manyfold it means that you
do believe that the coin will become popular in the next couple of years.
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.
Now regarding who has control of the escrow I think the devs would have to answer this instead of me.
It may sound cliche but " we will have to wait and see... "