There's no such decentralized in Ethereum network, it's centralized and Vitalik Butterin has full control over the network. If it's decentralized, we wouldn't see any news hacker can rob users money.
Wrapped Bitcoin doesn't have any value, they just following Bitcoin price.
It's true you can convert your WBTC to BTC, but it's depends on the WBTC's team if they want to convert it or not. Which mean if they turn to be scam, you don't have any way to convert it since they wouldn't want to convert your shitcoin (WBTC) to BTC.
WBTC is erc-20 a special token of ethereum. it first requires converting it to a native ethereum and then using a CEX to then convert fro ethereum to dollar or btc on a market
thus its a 3 step process
wbtc-erc20-eth-btc
yes wbtc team can decide not to allow conversions to native ethereum
yes ethereum team can change its code to lock up erc-20 as erc-20 and not convertible to native ethereum
yes CEX can delist ethereum