Unless they start doing things more efficiently the network will act to defend itself one way or the other against the SD "attack" whether through increased fees or blocking SD transactions altogether. SD may have to invest in its own mining equipment if it wants to continue its wasteful ways.
Bitcoin won't block S.DICE transactions. They are already paying twice the needed fee.
There's no such entity as a "Bitcoin" that can choose whether or not to block or not S.DICE transactions.
Any blocking would be done by individual pools. It would only take one large pool to actively be hostile to S.DICE to make them unable to allow zero-confirmation bets at all. If a pool discards S.DICE transactions but intentionally allows competing transactions from same source to process then the pool only needs a few % of network power for anyone to profitably attack S.DICE by trying to double-spend any losing bets - the few % of times the pool includes the double-spend (and cancels the losing bet) then outweigh the house edge on the rest of bets. You underestimate the extent to which some are opposed to S.DICE (not me - obviously).
It has become very clear that satoshidice is exacerbating problems in bitcoin. I think it has less to do with what satoshidice represents (gambling) than how they do things. It's the transaction spam. The problem is, they don't seem to care. I find this both ironic and sad, because it's costing them money and there are several easy ways around the problem. For one, not sending confirmations for losing bids would cut their traffic by over 30%, right? Right. But they insist on sending out confirmations on losing bids. Secondly, they could let people use accounts if they want to. This would speed things up from the user's standpoint (so there is a demand) and it would also save money in transaction fees. It would also enable them to add more games and expand their business beyond just the public address game. Also, there is absolutely no difference from a privacy standpoint. So not only would that save them money but it would cut the transaction spam by over 50%. But they haven't done that either.
Yes, "they have to fix it one day anyway". It's true, the blockchain is bitcoin's greatest weakness; people simply do not need 3+ years of cryptographic strength to prove they spent a dollar on an ice cream cone. But satoshidice transaction spam is the kind of thing that will hurt bitcoin before a solution can be found and adopted. Then again, it's only accelerating the obvious. When, not if, the blockchain gets too big (how big is too big?) too many people will be forced into web wallets or other centralized blockchain services, and they will not be able to play satoshidice. So satoshidice will then be forced to allow accounts or it will start losing money.
One wonders why they don't just do it now and save themselves (and us) the trouble.