“Essentially, (i) light client support, (ii) data sharding (aka “phase 1″) and (iii) the merge are all being specced in such a way as to be independent of each other, so each piece can be implemented ‘when ready’ regardless of what stage the other pieces are at,” ethereum’s co-founder Vitalik Buterin says.
Other devs concurred, with Danny Ryan, the ethereum 2.0 coordinator stating a merger testnet may be out soon:
“You can doc eth1 onto eth2 before you add sharded data availability or vice versa. The independence is allowing both of these efforts to be developed at the same time. We might even see an eth1/eth2 merge testnet in the relatively near future…”
However, this merger should not be expected any time soon with Justin Drake, an eth dev, stating:
“The Eth1-Eth2 merge is hard because it involves coordination between Eth1 and Eth2 and requires going against Eth1’s ossification. I don’t expect the Eth1-Eth2 merge to happen in 2021.”
So there is still some time to go, but as it stands, the current ethereum network will be merged in the Beacon chain itself, rather than as a shard. Developer Dankrad Feist says:
“Luckily, phase 0 does exactly what we need — it provides consensus. We will basically keep Eth1 as it is. Ideally it would be stateless by that time, so Eth2 nodes don’t have to take on full Eth1 validation, but it’s possible even without statelessness.
Sharding is not a requirement. In effect, it would just be a single shard, or (without statelessness) Eth1 execution would effectively run on the beacon chain.”
All these changes come as ethereans are asked to deposit to stake on the new blockchain while much in regards to what follows, including when they might be able to withdraw their eth, seems to be very in flux. Ethereum developer Carl Beekhuizen says:
“There is still a lot of development required before eth1 is ready to be connected to eth2 via a bridge. Eth1 nodes need to (at the very least) follow the finalised epochs from eth2.”
Such decision moreover would be a very big step for the ethereum ecosystem as a whole, including all the defi dapps and of course the miners.
Some miners are now moving to provide staking infrastructure, but it is difficult to see why they wouldn’t keep running the Proof of Work (PoW) chain, so effectively creating two coins and two networks.
That’s especially the case as Proof of Stake necessarily has tradeoffs, including a lower barrier to attack as it requires only 33% dishonesty, instead of 51% as in Proof of Work.
Moreover a small obscure bug can bring down the whole PoS network due to non-finality, while it is extremely difficult, if at all possible, to bring down the PoW network.
There are many other tradeoffs far too long to list, which suggests that without some scaling in PoS, the choice would be difficult for ethereans.