Even in the 1980s Reagan swept Northern New England. Vermonters might admire their distinguished Democratic governor -- the only one ever elected up till then -- but Democrats still looked like exotic outsiders. And now things are very different. Old parsimonious, Yankee Republican New England is gone. Migration, urbanization, and an appeal to remaining Yankee values on issues like the environment helped move Vermont and Maine into the Democrat column.
And now similar forces are moving VI, FL and maybe NC in the same direction. You could think of it as a continuation of the process that took MD and DE from the old Democratic South into the new Democratic East, or as the second stage of the process that led many Southern states away from the solid South towards a middle American Republicanism in the '50s, '60s and '70s.
By now, Northern Virginia looks more like the East than like the South, and its voting patterns will probably change accordingly, eventually pulling the rest of the state with it at least some of the time. It's not so different from the process that made VT or OR vote like NY.
That's not to say that as areas get more developed they always become more Democratic or more liberal or that the process is irreversible, but if the prevailing divide is urban vs. rural, some areas will give more votes to Democrats as they become more urbanized -- at least until the issues change again.
BTW, if you haven't seen it yet, you might appreciate W.J. Cash's view that the predominant cleavage in American politics would become East-West, rather than North-South, with the Democrats as the Eastern party. Cash was writing in 1928 in response to Prohibition and the Hoover-Smith race, but he's surprisingly relevant today.
x,
Your argument is severely lacking from the simple reality of social issues or infrastructure, as I like to call it. The reason VT, ME, NJ and OR have become more or less Democratic states doesn't just have to do with suburbs and other circumstantial elements. No, it has to do with the fact that voters in these states are fundamentally LIBERAL. Vermonters were James Jeffords Republicans just like Georgians used to be Zell Miller Democrats. Maine's popular Republicans are Snowe and Collins. Ideology plays a HUGE role in all this. Oregon and New Jersey have never been very conservative either. The main reason they flipped over is that liberal Republicans have become a dying breed and they don't like the modern Republican politicians. Gerald Ford did well in these states, but not George W. Bush - just like Jimmy Carter did better in the South than John Kerry. Carter wouldn't do well now because he's so much more liberal these days, but in the 1970s he was more conservative.
I'm not saying the South is immune to change, but I don't see a change really soon to the fundamental make-up of the region.
If demographics were a constant, that argument might be true. However, the liberal states will continue to lose electoral votes to the south as population continues to shift making the blue states more blue and the red states more red.