Do they now have no RKBA law that will stand up? They have claimed the current rules are standing for the next x days until they can come up with replacements. That means they could intend to bust you if you violate their old law. But you'd get off once you got in front of a judge. They'd still probably steal your gun.
Does that mean that I can carry THROUGH DC IAW FOPA? Legally, yes. Technically, you could prior to Heller. I would NOT have recommended it.
Does that mean that I can open-carry in DC? No. Heller didn't directly cover open carry. IANAL, so adjust accordingly.
Does that mean that, if I stay overnight in a public accommodation in DC, I can take a gun with me? Legally, yes. Technically, you could prior to Heller. I would NOT have recommended it.
I recognize the likelihood that any of these actions tomorrow, if discovered, would result in a takedown and hassle. Yep. If not shot. Give it 2-6 months before trying.
But what is the real-world significance of Heller? By itself, not much. De facto bans are illegal. DC's in specific. But that's like saying Omaha beach was just a couple hundred yards of sand. The tactical significance of Heller is that DC just got more gun friendly. Give it two to six months, and you'll be fine keeping a gun in your home or business with minimal police harassment. Starting today, you could keep a gun fully assembled and loaded in your home. But, you have to give the police, politicians and local judges time to adjust to their new reality. You'd eventually get off if caught, but you'd have to deal with a lot of harassment.
The strategic significance of Heller is it's a breach in the lines. We've lost a LOT of ground and have been in retreat since US vs Miller. It's a chance of taking some ground back. There are no certainty, but the odds just got a lot better.