There's also a difference between "can fill" and "must fill." Certainly you'll agree that most games don't aspire to as huge environs as GTA or MGS, and games can get away with being plenty big and plenty good looking even in GC's smaller medium. Certainly devs CAN spill well beyond DVD capabilities, but how many will WANT to, after factoring in all other costs/concerns?
It's not a matter *if* developers will spill beyond 4.9GB. Because they will for 95% of PS3 games. I fail to see how you think that your average ps3 game, with the thousands of high res textures, way way better sounds, well up to a billion polygons will just fit on a DVD when many ps2 games come close to filling up a DVD already.
I have no idea what they'll fit. Remember, if the PS3 is also upping the power tremendously, isn't it also going to be increasing its efficiency by a lot as well? We don't yet know how well the beast will handle texturing et al, it may be that the overall effect doesn't kick up the file sizes tremendously. This is yet ANOTHER thing we won't know enough about for quite some time.
Bigger textures, more polygons, better sound, bigger games = the need to go beyond a DVD. There are very few that argue this point.
I don't think ever started out as high, nor its medium as high as we're seeing right now. I also don't think it dropped down to negligence levels just two years afterward. (I haven't come across any all-encompassing data charts for DVD price history, but there's a decent article here to at least get an overview.) The lowest priced DVD players were $500 in '97 and just got under $200 in '99? Blu Ray players are at WHAT right now? I certainly think BR will go WAYYYYY down, but it remains to be seen whether it will hit consumer-grade levels by the time the PS3 is in production.
Blu-ray is only expensive because sony can infact get away with it. There is no competition out there, if someone WANTS a blu-ray player now they have no choice but to pay the outrageous price issued by the select few that have the players out on the market.
I bring you this quote from Sony, they agree with me.
"Sony also sees the blue-laser technology as key to next-generation game machines, whose advanced graphics will require huge amounts of storage capacity, a spokesman said"
quote from Reuters, 03.31.03, 2:33 AM ET
I'm just not willing to think Sony will paint themselves into a corner with it should Blu Ray still be quite an issue price-wise. I'm certainly they WANT it to be a part, but I'm also certain they're not going to place all bets on it HAVING to be, nor that they would be willing to take immense losses to assure it being there.
You still havent listed any other mediums that can be used for PS3, as DVD's won't cut it.
Oh and not to mention, blu-ray can function as a HDD becuase it's rewriteable thus killing two birds with one stone.