Yeah, I think Raley Field is too small (albeit not for the crowds the A's have been drawing in Oakland, but if they moved to Sacramento, there would be huge local interest). OTOH, if they got a commitment to build a full-size park over in the rail-yard, they conceivably could play in an undersized park for a year (a la the Giants at Seals Stadium before Candlestick was finished). But in fact they'd probably just stay in Oakland until a new home was ready.

In any event, despite what seems like a very likely winner for many people (not everyone, I admit), I don't see it happening in any combination.