Yes there is trustless and decentralized bridge theoretically possible. Polkadot have Hyperbridge and Snowfork , maybe these tech can be adopted for Grin somehow.
Grin can be bridged to Polkadot AssetHub and can be used at any DOT chain, including Hydration the #1 DEX on Polkadot with 300M TVL. Grin can be traded on dex and returned to native chain- it is opening a lot of possible use cases, and more freedom.