Yes, there is a limit, because we sense taste with specific taste receptors on our tongue and there is only a finite number of them. So, once they are all being saturated, any more of the same taste won’t make a difference.
I suppose this may be limited by our taste buds. People differ in how sweet or sour things taste to them, so our brains differ in how these tastes get processed. It may be similar to a limit on how ‘red’ something can look; it depends on our eyes.
Yes, there are only a certain number of each type of taste bud and each taste bud has a limit of sensitivity. Kind of like if something is warm you can bare to touch it, but if it keeps getting hotter, you can’t bare it any longer – that’s the limit of sensitivity. If the taste buds are so flooded by sweet or sour etc, they will no longer taste anything that is more sour or more sweet – they will taste the same sweetness or sourness as the last.