It is almost a software change provided the TV is capable of a high framerate.
Alas, Sony et al made it a hardware issue, requiring re-purchase of recently-purchased HD hardware and requiring the most expensive & annoying forms where possible (battery-powered high-price easily-lost/broken glasses). This when a relatively cheap polarizing overlay with passive glasses (heck, contacts even) would have made it a no-brainer upgrade.
Polarsising screens would have had greater cost increase on the TV. Your complaint seems to be that they didn't go all in an put the cost in the TV. The Active glasses can fit over normal glasses. The first year the glasses had button batteries, after that they were USB rechargable (and compatible with the first year too).
Passive glasses would also have reduced the resolution although that might be a worthwhile tradeoff.
I'm not sure what alternative you suggest they should have done differently to avoid "requiring re-purchasse" of hardware. PS3 was software updated to support 3D Blu-ray and 3D games. You might have to avoid existing AV receivers to get the 3D signal through which isn't ideal but not sure how avoidable it would be without making the user manually set up the 3D each time they wanted it and losing half the resolution by putting both frames in a single frame.
Think: polarizing screen overlay, sensor in corner watching subtle pixel indication of which eye to show. No need to repurchase TV, just buy stick-on overlay. Cheap passive glasses.
Alas, Sony et al made it a hardware issue, requiring re-purchase of recently-purchased HD hardware and requiring the most expensive & annoying forms where possible (battery-powered high-price easily-lost/broken glasses). This when a relatively cheap polarizing overlay with passive glasses (heck, contacts even) would have made it a no-brainer upgrade.