I'd like to note that if it were to support sdtvs, then you wouldn't see a difference graphics wise from the current generation. The reason why the current gen actually looks okay on an sdtv is that usually the actual resolutions of the games is a bit higher than 480p and slightly below 720p. They scale them up on higher definition tvs. Which is why there really isn't a huge difference between playing many xbox or ps3 games on a 720p tv or a 1080p tv. On games that are actually native 1080p the difference is pretty large
On games that aren't scaled the difference between playing on an hdtv and a sdtv is huge.
There is no point in buying a new console if they won't see any difference in display. There is more than a big enough library of games to play in the current generation that look just great on sdtvs.
Even if they did supply it you would complain that there isn't enough of a difference between the current generation and the next one.
for example
Take this
and compare it to this
That isn't even that high fidelity of a game and you can see a huge difference between them. And on both of them all settings are to max except resolution.
It gets even worse when it has to be stretched out further to match a bigger screen.
compare this
With this
And that is with everything but resolution maxed out.
For a further comparison try
with this
To really understand the difference you have to view the images fullscreen zoomed in (copy the image link and then follow it to imgur. There you can zoom in your view until it takes up all of your screen) enough to take up your whole screen. If your screen is that low res i'm sorry there is nothing I can do to help you.
The image should look good if you keep it small, but when you force it to take up the whole screen you can easily see the difference.
The lower res images were taken at 720x576 and the higher at 1920x1080 resolution. That is the comparison between playing a modern game on standard resolution vs high definition at max settings. That means with all the detail they put, without the resolution behind it, it doesn't look that great.
Basically if you buy a ps4 and play games on your sdtv with it, you will only see a few little details better than what you get with your ps3. It definitely will not be worth the price you pay for the console.
Microsoft shouldn't be catering to people with sdtv because if they do they will just get complaints that there isn't enough improvement to justify the costs