The Ethereum (ETH) 2.0 proof-of-stake (PoS) transition will not take place until 2021, the CEO of crypto analytics firm Messari predicted at a panel of ConsenSys’ Ethereal Summit on May 10.

During the panel titled “The Smart Contract War Is Coming,” Messari’s Ryan Selkis pointed out major risks associated with Ethereum’s migration from a proof-of-work (PoW) to a PoS consensus algorithm, arguing that PoS systems “are not proven to work.”

According to Selkis, the currently PoW consensus algorithm of ethereum 1.x, is “probably pretty good, and maybe even good enough.” The expert elaborated that the algorithm is well-established, having proven itself in the last decade with bitcoin (BTC), as well as ethereum in the last several years.

Selkis forecasted that the PoW algorithm will be a status quo for “at least two or three years,” while the ethereum PoS transition will “take a lot longer than anybody appreciates.” He stated:

“I don’t expect Proof-of-Stake and ethereum 2.0 to happen before the end of 2021 at the earliest.”

The Ethereum blockchain’s transition from PoW to PoS is one of the most discussed and anticipated events in the crypto community. The shift should purportedly bring more scalability, security and economic efficiency. PoS is also purported to be more energy efficient than PoW.

On May 7, sharding development firm Prysmatic Labs reported that an Ethereum 2.0 PoS test beacon blockchain was live. As Ethereum core developers said earlier in May, Ethereum’s first-stage transition to a PoS consensus algorithm could be completed by June 30, 2019.