Right, ArgentX or Braavos will both provide the Provider that you defined in your other post. [SNIP] Starknet Provider JavaScript API - #8 by ltoussaint
My thinking is that as long as that proposal gets implemented then both wallets can communicate over the same JSON-RPC API then it should be possible for the DAPP developers to just do:
const provider = new starknet.Provider(window.starknet);
const accounts: AccountInterface[] = await provider.getAccounts();
Of course, this could be up to starknet.js to facilitate, not necessarily the API. Translation from the JSON-RPC API to AccountInterface which the users use could be handled internally by starknet.js.
Or atleast thats one way in which I think we could have an API that more wallets could implement without breaking the things that already work 