The EOD reconciliation (and corresponding inability to settle a position in milliseconds) is a feature - it allows "obvious erroneous trade" roll-back mechanisms, etc.

Very few people want the financial system to be a contractual suicide pact - they want it to be predictable, but when the unpredictable happens - they want the retail and institutional investor to be protected (the HFT players can go beat each other up - no one will really cry about them). And unpredictable can be anything from a power event taking out multiple exchanges in the NJ triangle (Sandy hurricane) to a cyber-attack (never happened yet) to a flash-crash driven by algorithms from multiple HFT driving each other nuts (happened at least once).

So, it is not EOD processes as such, but the ability to pause, assess the entire system holistically, and then correct it before it blows up the portfolios of everyone holding a 401k. So even though the exchanges _could_ got to 24/7 trading, I'd be surprised if we just went away from cyclical 24-hr based windows of settlement.