It would be worse, because your TV has to upscale the resolution to it's naive 4k.
Here's an example:
Now look at the size of the SD picture, compared to the size of the UHD picture. Your TV has to fill in all those missing pixels if you want to watch it in full screen.
You could theoretically watch SD at better quality, but it would be it's naive shrunken size, and not full screen.
The solution is to start watching higher resolution content. It was the same problem we faced when moving from SD to HD...