Hello.
According to Charles tweet, there will be testnet, we can try. But, for ex. if I mostly interested in Plutus development, is it important to me?
Is it a testnet, with a Plutus support, or other new experimental features worth to try? May be there is a spec somewhere?
Thx.
The upcoming testnet is for the Shelley stage of the project. This introduces staking with a view to decentralisation once it goes to mainnet.
Plutus is being introduced as part of the Goguen phase, which is on a parallel path. No announcements for the timeline on Goguen yet, but a new roadmap is being published soon at https://cardanoroadmap.com/.
So to answer your question the immediate testnet announcement doesn’t relate to Plutus.
Have you tried the Plutus Playground at https://testnet.iohkdev.io/plutus/tools/playground/