In addition to proposing community updates to versions V0.12.3 and V0.13.0, Starknet intends to move its testnet from Goerli to Sepolia following its deprecation. Support for the Goerli testnet will continue through the end of 2023. While V0.13.0 will feature a new transaction type V3, V0.12.3 will deprecate feeder gateways and modify the __validate__ of account contracts. With the exception of ETH, fee markets, paymaster, and nonce generalisation, this transaction type will establish the framework for STRK transaction fees payment.
Furthermore, Cairo version 2.4.0 7—which includes string literals and fundamental string operations—will be included in V0.13.0. The following is the upgrade timeline: V0.12.3 Goerli testnet upgrade on November 19; V0.12.3 mainnet upgrade on December 11 (one week earlier than originally scheduled); V0.13.0 Goerli testnet upgrade on December 5 (possibly postponed until December 13); and V0.13.0 mainnet upgrade on January 22, 2024 (pending governance voting).
On November 15th, Starknet will start moving over to the Sepolia testnet. Full nodes, API services, SDKs, and other Starknet development tools will start moving to Sepolia at that point as well.