This is pretty far in the future, so we can only speculate, really.
For example, let's say that EA buys Take Two. They whore out GTA right away. GTAV launches Xmas 2009 for Wii, DS, 360, PS2, PS3, PSP and Mobile. First week WW sales are...
360- 3M
PS3- 3M
Wii- 2M
PS2- 500K
PSP- 500K
DS- 500K
Mobile- 500K
Totalling 10M. Lifetime sales reach 12M. GTAVI is launched Xmas 2010, and sells half as much. GTAVII is launched Xmas 2011, and is actually available for more formats than the total number of copies it sells.
Or, let's say Ubisoft and Take 2 merge. Take 2 releases GTAIV-2 in 2011 for PS3 and 360. The game does similarly overall to GTAIV. After the world is destroyed in 2012, GTAV is never released.
Or, let's say Take 2 sells it's soul to the devil to avoid a merger. But of course they don't read the fine print, and end up forced to develop only for Wii. After listening to analysts who inform them that Wii has "a different type of customer," they release "Grand Theft Auto V: MyCarnival Baby Racing" in time for Xmas 2008. The game moves 1M units first week and has good legs, but results in 6 more months worth of articles bashing Wii for poor third party sales.
"[Our former customers] are unable to find software which they WANT to play."
"The way to solve this problem lies in how to communicate what kind of games [they CAN play]."
Satoru Iwata, Nintendo President. Only slightly paraphrased.
