Will he keep us up - likely, I think any semi competent manager would.
If he does will he simply say so long and leave, for me hugely unlikely - Moyes has wanted back at the club for years - if he gets back sure as hell he will do everything to cling onto it once he is.
Will he be the right men to rebuild the team, I doubt it seriously - since Moyes was here first time recruitment has moved onto a different level with vast scouting networks now being commonplace as well as data analyst companies specialising in this field. The days of a manager drawing up a few lists on a board and going and getting them has long had its day.
Throw in you should with rare exceptions 'never go back' - there's a damned good reason it's a well known expression, because it's nearly always true that second time round is never ever as good and often a disaster (be that football managers, players or life).
I said also on the Mourinho thread, that perception does matter hugely, and the way this will be perceived will cement the club as still stuck in the blue Bill era in spirit if not name
Lastly can't get past after a sleep and last night's beer the simple fact he pissed all over us the last year he was here and his true feelings about the club really came out then and when he left.
Moyes never really got the club, he was just very good at presenting a face to the fans and media like he did, but a lot of the small time mentality instilled in us these days traces right back to Moyes tenure here.