In response to the article posted regarding the announcement of the list of games to be shown at this year's Tokyo Game Show. Konami Digital Entertainment Co., Ltm. has opened a website to correspond with the Konami official announcements that will occur simultaneously as the event.
The list of games posted on the front page were also listed on the "special site," though new games have been added to the list. The "special site" has sections opened for series and franchises of their most popular and anticipated games. Under the Silent Hill (サイレントヒル) section, you'll find the section pertaining to Silent Hill 0rigins (Silent Hill Zer0) which lists that the game will be a prequel to the series. (Nothing new there.)
As such, you'll notice that the site is currently still under construction, which means that the list released so far is only a preliminary list of games to be shown at TGS2007. This suggests that if Silent Hill 5 is to appear at TGS2007, it is still unannounced. Please note that the "special site" is not an official indication of all the Konami games that will appear at this year's TGS, but only the games that will have corresponding web content to post during the event.
Silent Hill 5 may be shown at TGS2007, but the "special site" indicates that there will not be any corresponding web content shown on the official Japanese site. Perhaps there may be another place that will post the information...?
The current list of games featured on the Konami Special Site are: Metal Gear Metal Gear Solid 4: Guns of the Patriots (PS3) Metal Gear Online (PS3) Metal Gear Solid 2: Bande Dessinee (PSP) Metal Gear Solid: Portable Ops + (PSP) Metal Gear Solid Mobile