Yes.

This isn't even really a question. Just with Gran Turismo 5 or just with a $100 price cut PS3 would likely overtake 360 in Total Other sales by this time next year.

With both, 360 may quite possibly never manage to outsell PS3 in Others again and the difference could be gone by January.

The same holds true for Japan, but simply replace the words Gran Turismo 5 with Final Fantasy XIII.

Definitely. Europe loves Sony, Europe loves GT, and Europe loves cheap things

Easily. Didn't the PS3 catch up to the 360 in Europe at some point? Despite that 16 month head start the 360 had. We all know Europe are big Playstation/GT fanboys, the PS3 would do fantastically well with a slim & GT 5.

Actually, in Europe, the 360 only has about a 400k lead, as the 360 has an 800k lead in other others and another 200k in Australia
And yes, I do think that it will bring the PS3 up to and past the 360

No, 360 would immediately fight back (and it has more market power).

Plus :

the most loyal fans already own a PS3
the Playstation brand has been degraded
while the XBOX one gained some consideration
Wii still works like a buffer zone

You contradict yourself. Only to the most loyal of fans has the PS brand been degraded. A casual fan doesn't think of PS and think any less of it now.

The most loyal already own it, as do technology junkies. What's left is people who already own another system, gaming newcomers, casual fans, and parents. The reason that people who already own other systems don't own a PS3 is usually because of price; gaming newcomers would be much, MUCH more likely to buy a PS3 if the price is $100 cheaper than if it remains at the same price, so that can only help sales as well; parents[as demonstrated in burgrimmar(sp.?)'s post] can be talked out of purchasing a PS3 for their child simply because of the steeper price, so a more level price would help in that regard; and casuals wouldn't chip out $400+ to buy a system, so a price cut would help that cause also.

Sales will explode with a $100 price cut.

@OP:
IMVHO yes. It looks to me too that a substantial share of PS3 critics are just angry for its price, so PS3 hate would decrease. And a lower price would increase synergy with Blu-Ray, both with the obvious mechanism of HW sales increasing media sales and vice versa and also easing mutual justification for HW purchase from its two main functions.

Yeah...it would. Europe is GT5 territory.