How will sending bundles change in PoS Ethereum?

Sending bundles will feel very much the same as it does with Flashbots PoW Ethereum infrastructure. You’ll still be able to send & simulate atomic bundles, and use the same bidding strategies in the blockspace/MEV auction.

The real difference is in the backend architecture.

relay.flashbots.net (where bundles are sent in PoW Ethereum) will send bundles to the Flashbots builder after the merge. On the searcher side, the method for sending bundles to flashbots doesn’t change at all. All Flashbots relay endpoints from PoW Ethereum will be the same post-merge.

With PBS, you may want to send bundles to more builders than just Flashbots. Other builders will need to implement their own version of this bundle relay to accept bundles, but as long as other builders adhere to the same API specification as Flashbots, you can use existing Flashbots client libraries to interact with these builders.