I don't think it matters much even if the spammers have infinite money and just keep on doing this without stopping. If that is the case, then we'll just have to raise the default transaction price and increase the mining reward so that enough miners get on it to bring the confirmation time back down.

any spike in transaction spamming should in theory be met with an equal spike in increased hashpower going for the higher mining rewards, and it should all even out in the end.