A New price tag,and some badass games that are to be announced yet.
Uuncharted 3?Kilzone 3?Resistance 3?GT 6?Just to name a few.

Well, there's still Final Fantasy XIII Versus, Call of Duty Next 1, Next 2, and Next 3, inFamous 2, Uncharted 3. Plus a few more new IP's and multiplats.

Not to mention it's still $299, so it's got another price cut before sales start dying down into next gen.

The obvious answer is games, lower price, and an even more aggressive ad campaign.

lol its got at least another two price cuts up it's sleves, or if it just keeps on reducing the price by £50 then it has lots of price cuts up it sleves, that is one big thing in it's favour the xbox 360 doesn't have as much room for price cuts, lol, and anymore will make it look like the final reduction before they release a new model lol
then we have the ps3 super slim, as people have said the slim was just a way of reducing costs, i think we shall see another better version of the ps3 to come yet.
as for games, i don't think they will ever stuggle you only have to look at ps2 and ps1 to be reminded of the amazing games they kept on pushing out every year.
finally the motion control will be a nice addition (for me) and should help to kepp momentum up (new games with motion controls, hopefully good ones lol)
i really don't think sony has anything to worry about except natal, but i think natal will be a quick fad and then flop when people find out it does everything the pseye already does lol

about the price cut :

STOP believe that there will be a new price cut anytime soon

the next price cut will be 50$ AT VERY MAX and will take place in 2011 at best !

the only I can see in 2010 is heavy bundle offer

2006: PS3s Price is way too high its DOOMED!

2007: Halo 3 is out PS3 IS DOOMED

2008: MGS4 just released PS3 HAS NO MORE GAMES ITS DOOMED

2009: Killzone 2 is out it has no more games ! ITS DOOMEDER!

2010: God of war 3 is out Xbox360 is DOOMED ! lol ;P just kidding , please don't hit me.

@ title question
1. Good Games
2. Good Marketing
3. Competitive pricing

Edit: dang I thought I was being original. Still, at least I know I'm right.

I find it amazing how Microsoft has the Elite priced at $300.
One advantage Microsoft seemingly may have here is how they could add a blu-ray player, or built in wifi to the console, and introduce a new sku at a higher price, this then would give them more room for price cuts in the future.
Except there is one very large problem with that, they are too late. The PS3 would be cheaper if all the specs matched, and people would start making comparisons that would not shed a favorable light on MS.

With that being said, Sony will stay in the game by introducing a new sku down the line that increases the allure of the hardware in some way.
The obvious one is a motion bundle, where the price of the motion PS3 would probably be introduced at $350, then a "price cut" later to $300.
That is 2 separate bumps in sales without decreasing the current price of the console.

At the time the motion bundle lowers to $300, an ultimate sku type console would come out and replace the $350 price point. Such a sku would need to have 500gb and PS2 bc alongside motion inclusion, it could come with an hdmi cord and remote. all for the bargain price of $350.

This is another bump in sales that would happen simultaneously as the 2nd bump.

Then the sku discussed above would lower to $300, and become the default $300 sku.
BOOM!
3rd bump in sales, (similar to MS's move where the Elite became $300)

All of this is accomplished before Sony dips below $300.

The simple fact is PS3 is still not at mass market price.....that alone means momentum will increase when it gets to that price

apart from that?

The Agent, FF13, GT5, Motion Controls

Now that the PS3 is on fire, it will be difficult to stop the momentum the platform has now.

It's always been games that drive a system to success. The PS3 has the added benefit of being "future proof". PS3 I feel will last longer on the market without it's successor than the PS2 did, which was still 6 years.

Anyway, Playstation Sphere, the strong first and third party line-up next year, added services and features we don't know about yet.

Playstation 2 become the top system of all time based mainly on games. The PS3 has that strong support now and it can get new features and services with a flip of a switch.

Word of mouth and change of perception will keep its momentum high. If the new buyers don't enjoy their PS3's, then the brand will suffer badly.