I'm no technical expert, but how will Boeing get around the world and update the aircraft and sims? It's not as though you're updating IOS or Windows. Additionally the longer the aircraft are grounded the more rigorous the checks will have to be before they're allowed back in the sky with passengers.
Surely pilots will have to be retrained and the CAA etc will have to approve the updates, something that seems to have been lacking on the part of Boeing. I can't see them taking to the skies during this summer season. There is also the problem of passenger confidence, many talk of refusing to fly onboard. Intersting times ahead.