Yep, the reason I see them trending left is due to increasing Latino (and to a lesser extent) Asian populations. Immigrants and minorities typically tend to vote Democratic, so that should make AZ and TX more Democratic in the future.
I don't think that's going to be as big of a factor as you might think. Consider that the Democrats have been slowly bleeding Hispanic support in Texas, dropping from the mid-to-high 70s in the 1980s to roughly 60% now. It's one of the reasons why Obama lost Texas by roughly the same margin that Micheal Dukakis did, despite the fact that the state gained almost 5 million Hispanics in that time frame.
That's not to say that the Democrats can't swing Texas into their column, but unless they can improve on their percentages in either the White or Hispanic vote, they'll need about 10 Million* more Hispanics in Texas (or essentially turning it 50% Hispanic) to flip the state.
*Assuming Hispanics comprised ~25% of Texas voters, and voted for Obama ~63%-37%, than that means Hispanics only gave Obama about a 500,000 vote edge. So in terms of adding politically identical Hispanics, the Democrats would need about 18 Million more in the State in order for Obama to win it. Add in increased turnout numbers, and I could see that figure dropping to only around 10 Million.
