Never say never.
360 will almost definitely be back on top for at least a week or two following it's next major price drop. Barring a price change though, it's going to have a hard time beating the PS3. Just looking at the upcoming releases this year, Microsoft only has four exclusive releases that could push any noticable amount of hardware.
-Halo 3: ODST (Sept. 22 NA/EU, Sept. 24 JP)
-Forza Motorsport 3 (Oct. 27 NA, Oct. 23 EU, Oct. 22 JP)
-Grand Theft Auto: Episodes from Liberty City (Oct. 29 NA/EU)
-Left 4 Dead 2 (Nov. 17 NA/EU)
Halo 3: ODST potential to sell a ton of hardware is doubtful, though it should at least raise weekly sales by 25k given it's worldwide launch. Forza 3 and GTA are both launching back to back during the last two weeks of October so it gives Microsoft a good chance to rise in sales, but Sony has Uncharted 2 launching the week prior and Ratchet & Clank, FIFA 10, PES, and Tekken 6 during those two weeks to likely keep it ahead of 360. Left 4 Dead 2 is launching alongside Assassin's Creed II which is a multiplatform game that should see the majority of it's sales from 360, however by November 17th Christmas shopping and sales will be well underway and any mild increase do to software will be completely unnoticable. It's also worth mentioning that none of those games will push hardware in Japan. Microsoft is without a single big Japanese release this year.
If I were to choose a week when the 360 has the greatest chance of outselling the PS3, it would probably be the week of Modern Warfare 2's release. Sony doesn't have any major games releasing exclusive for PS3 during this time.
