Blockstream's sidechain, called Liquid, also went live last month, and it's "L-BTC" sidechain token is supported and backed by 23 Bitcoin exchanges and services.
Does anyone have any opinions? I believe Bitcoin users will be moving away from main chain transactions for more speed and privacy, but move back to the main chain for storing for more security.
Blockstream's Liquid and Rootstock are federated sidechains - they are pretty trivial to implement as the peg and the blockchain maintainance is managed by a group of companies. The challenge is to find trustworthy members for the "federation" holding the multisig accounts.
However, Liquid/Rootstock may have interesting use cases - mainly for transfers between exchanges and service providers, which seems to be their main purpose.
The "Drivechain" model is more interesting for me as the peg in this case is maintained by miners, and thus is, in theory, decentralized. In the case most Bitcoin miners mine the sidechain too, the attack cost for the sidechain should be similar to the attack cost of Bitcoin's main chain itself.
I agree that - once transaction fees rise again - sidechains and LN could largely replace mainchain transactions for the general public, if they're implemented in a proper way, i.e. in an easy-to-use GUI client. LN would be used for microtransactions, sidechains for most mid-tier transactions and the mainchain only for the bigger ones (settlements, real estate investments etc.).
One thing about "sidechains" is that they don't really need to be blockchains. You could use a normal database and store hashes of that data on the mainchain. I think that is very efficient.
But wouldn't you need a centralized entity to inscribe the hash data in the main blockchain? Otherwise, there should be a double-spend risk with this approach, or you would have to inscribe each single transaction in the main chain, too ....