Hi, I'm new to this forum and this is my first post. Everyone's been discussing wether the next game will take place in a European city, or in another USA city, etc... Personally, I feel that the only city in America to hold as high an interest as New York, Miami, Los Angeles, San Francisco and Las Vegas, both in terms of international awareness and of what R* can do within that setting, is Washington D.C. 
But I am also aware that there are some of you who'd prefer this game to have an international city as backdrop, like London, Mexico City, Tokyo, etc... And that's how I spent most of an afternoon coming up with this personal concept for GTA 4 - it's mostly Tomb Raider style, in that the main character gets to travel all around the world doing "jobs" for several colorful characters. 
Along the way, the main character would stop by Capitol City (D.C.), Texico City, Pokyo, Blundon, Amusterdam, and Rio de Fevereiro. Just imagine the vastness of comical situations and social satyre that R* could pull off with this! The next GTA will surely come out on Next Gen consoles, so being only about one third bigger than GTASA won't be much of a problem... PS3 can handle that. Plus, R* could go nuts when making all the funny satyre for us fans to enjoy...! It'd be the ultimate satyrical adventure, they'd have their hands full with this one... 
Plus, there's just something about playing as an international hired gun (like, James Bond or Alias-style) that makes my inner self grin widely. 
Without further ado, here are my regional areas for each city: 
CAPITOL CITY 
Adams Intl. Airport 
Arcadia 
Australia War Memorial 
Capitol Heights 
Fairwood 
Fairwood Park 
Federal Avenue 
Jefferson 
Lincoln 
Lincoln Station 
National Museum 
Newburg 
Seven Stars Golf Course 
Watergate 
White Hall 
Wilmington 
Wilmington Airfield 
Wisteria 
TEXICO CITY 
Armadillo 
Barrio Azteca 
Cardoso 
Cienfuegos 
El Cielo 
Juarez Intl. Airport 
Las Condesas 
Las Rubias 
Pueblo 
Salinas 
San Juan 
San Pedro 
Santa Carmen 
Tateloco 
BLUNDON 
Blackgate 
Blackgate Cathedral 
Blackgate Tower 
Blundon Bridge 
Canal City 
Central Blundon 
Chapel Cross 
Chelsea 
Docks 
East Blundon 
Gravesbury 
King James Park 
Oarsmouth 
Oxminster 
Saint Michael 
South Blundon 
Victoria Road 
Victoria Intl. Airport 
West Blundon 
Worcester 
AMUSTARDAM 
Amstrecht 
Arnhem 
Arnhem Campus 
Barkstad 
Bitrecht 
Bosch Intl. Airport 
Canaalstad 
Friburg 
Haangover 
Haarlem 
Kokenhof 
Leidenstad 
Little Antwerp 
Munster 
Munster Island 
Noord Amustardam 
Old Haaven 
Pottsdam 
Trisburg 
Wasserstad 
POKYO CITY 
Amatsu 
East Pokyo 
Downtown 
Higashima Island 
Kato Island 
Kokyo 
Meguro Intl. Airport 
Mikkado 
Mizuya 
Mount Fujimori 
Pokyo Bay 
Pokyo Port 
Roppongi 
Shibuya 
Shijuko 
West Pokyo 
Yaganashi 
RIO DE FEVEREIRO 
Bairro da Fajuta 
Botafogo 
Carioca 
Central Rio 
Central Station 
Copabacana 
Downtown 
Estacio 
Guanabara Intl. Airport 
Guanabara Bay 
Ipiranga 
Rio Norte 
Rio Sul 
Saara 
Santa Pureza 
Sao Catarino 
Sao Jacinto 
Villa Nova 
I might come up with maps for these cities someday. They'd all be connected by airports, of course, with limited mobility out of each of them like in GTA 3 and GTAVC... Now I urge you people to comment on this, especially folks living in each of these cities (D.C., Mexico City, Rio de Janeiro, London, Amsterdam and Tokyo). I might expand on this concept more with my ideas for vehicles, missions, storyline, etc... 
But I need opinions, people!