I will attempt to get you all up to speed with the details regarding the next Fallout.
Interplay doesn't exist anymore. They filed for bankruptcy a long time ago and Black Isle Studios, responsible for the originals, have since disbanded. A new studio was created from it's ashes though, called Obsidian Entertainment. They are the developers of New Vegas, and were given the rights to make this game from Bethesda. It will use a reworked version of the Gamebryo engine, found in Oblivion and Fallout 3, and will be pretty much play the same, with some new advances.
The storyline follows a young man (or woman) who was buried alive in the Nevada desert. A robot digs them up and takes them to it's master, who revives the player and gives him a Pipboy and Vault jumpsuit, as he was once a Vault dweller. The player must then face the hordes and horrors of the Wasteland, including Super Mutants, Ghouls, Raiders and Slavers. What's more, the New California Republic, a major faction in the originals, returns and is looking towards New Vegas for the conquer. New Vegas, a city rather untouched by the bombs, is a the last thriving city in the Wasteland, and is an exclusive party. The main story will revolve around Caesar's Legion slavers, the NCR and the local militia of New Vegas. Caught in the middle is the player, and all around him is death and destruction. Fight to survive.
I always considered Fallout 2 to have the best storyline of all the games, including 3 and Tactics. Having the original devs behind New Vegas should make for an impressing plot I believe. I do have a good deal of questions, like "Will the Brotherhood be in it?" or "Where's the Enclave?" The latter I hope will be answered with "They're not in it." The Enclave are pretty owned right now, and I'd hate to make them just another faction that will always show up in Fallout. It was chilling when they showed up in Fallout 2, and epic when they hit up D.C. They should be saved for the most badass moments, and not overused. The Brotherhood however are almost a staple of the series. There's always a Pipboy, the player always wears a Vaultsuit, and the Brotherhood are there. It'll be interesting to see the original West coast douchebag BoS as opposed to the nice BoS in D.C.
So overall, I am super stoked for New Vegas and am planning on celebrating the release in Hardcore style. Playing Fallout 3 all day and then go to the midnight launch wearing my Vault jumpsuit. I will nerd out.