As usual, everyone overestimates the boost created by big releases. I've had to say it so many times, I should probably put this in my sig: "Hardware never spikes as much as you think for big games." 
With that said, 360 and PS3 hardware WILL be up noticeably for the week of Grand Theft Auto (which of course is next week's charts, not this current upcoming one). I expect both to see something in the area of 30% rise, with perhaps as high as 50% as the extreme upper limit. But some of these predictions - 300k? 400k?! - are just lunacy.
Fun fact: neither the PS3 nor 360 has ever topped 250k in weekly sales outside holidays/PS3 European launch. This is easily seen by looking at our weekly sales chart:
http://vgchartz.com/hwcomps.php?cons1=Wii®1=All&cons2=PS3®2=All&cons3=X360®3=All&start=39047&end=39558
The 360's best was a 241k week for Halo release last year. The PS3's best was 228k last month on the week of 28 March, the debut of Gran Turismo Prologue in Europe. Clearly the release of large titles do increase hardware sales - they just create "bumps" on the graphs, not wild spikes upwards. And we'll see the same thing for Grand Theft Auto. There's a good chance that both the PS3 and 360 will top their previous non-holiday high marks that I mentioned above. But there's very little chance that they'll get anywhere close to 300k weekly sales (which would be an 80% increase for the PS3, and about a 110% increase for the 360!)
The Wii has sold 5.251m units so far this year, across 16 weeks; that's an average of 328k per week. So as long as the Wii sells around its weekly average (which it certainly should do!) there's practically no chance that it will be outsold by either the 360 or PS3. You can't guarantee anything in the market, but statistically the continuation of Wii hardware dominance is extremely likely.
End of 2008 totals: Wii 42m, 360 24m, PS3 18.5m (made Jan. 4, 2008)
