So far the limit has been capped at 100MB, but recently it looks like Apple has decided to increase that limit to 150MB. This means that if you’re using cellular data to download your apps, the biggest you can now go to is 150MB, 50MB more than what was previously allowed. The difference isn’t that big, but it should afford users some flexibility in the future.
Those using unlimited data plans probably won’t be affected by this change, but those who do have data allowances should probably pay attention to these changes. Given that with the iPhone X Apple has increased the display resolution, it also means that app developers can take advantage of it by increasing the texture resolutions in their apps which could also mean bigger download sizes, so in a way it makes sense that Apple has increased the limit to potentially accommodate for those changes.