There's always the chance that some new issue – immigration? Iran? cap and trade? something nobody has thought of yet? – will blow up and bring the GOP back to life.
It's not clear why Grunwald mentions immigration. Earlier, he cites the GOP's allegedly impending demographic doom without showing any awareness that the problem is wholly caused by immigration policy. Maybe he's a sort of political idiot savant, able to come up with disconnected insights, just as Dick Morris suggested the immigration issue could work electorally in 2004 and 1996 although eveything he writes on immigration in principle is useless.
Whatever - it's a good sign!