Theta Mainnet 4.0 Theta Metachain - Q422
Why - Theta has designed its next major upgrade to meet the needs of Web3 and allow permissionless horizontal scaling of the Theta blockchain network.
What - Theta's 4.0 Mainnet release will be called "Theta Metachain". The purpose will allow Theta to become a Chain of Chains or put another way an interconnected blockchain. Think of it this way - a main chain with unlimited subchains underneath it allowing for massive scale and transaction(s) support. All the while, chain and subchains are fully EVM compatible and allows you to select your gas (TFUEL over ETH) for lower transaction costs.

When - Theta has been rather vague and just stating it will be available in Q4 of 2022
Competition - Avalanche, Cosmos and Polkadot already have very similar design structures currently in place with their subnets and subchains.
Theta Metachain Whitepaper - https://assets.thetatoken.org/theta-mainnet-4-whitepaper.pdf
What's missing from this announcement? SNARK-proofing, perhaps we will get this in a future release from Theta.
Summary - Well you know I am a big fan of Theta and their continued development put into their Mainnet 4.0 (Theta Metachain) will allow Theta to meet the scaling and massive transaction demands from Web3.0 offerings, all while continuing to bring more value to THETA and TFUEL.
Disclaimer - I am not an employee nor an agent of Theta Network, although it sounds super exciting!