Well since now nvidia owns all of 3dfx's intelectual property portfolio, they can design their next chip to be capable of scalable architecture, but i dont think they will, since producing dual boards it not cheap. and they can have the best performing card with only one chip. remember 3dfx resorted to this solution only because they couldnt compete with nvidia using only one chip (the vsa-100 was crap comparing to a GF). now if there will be a revised kyro with great fully programmable t&l, and same specs as next-gen GF, but because of the tyle rendering it will outperform the GF, nvidia will have to make the GF capable of dual (or quad) rendering.
the next (5500) kyro chip doesnt look like a nv30 killer to me, but the next-next generation, ohh well no one really knows that far. we'll just have to wait and see what happens.