Yes, they are safe from this because I have never seen anything in the Quran that says the age of humans or the earth. And they can defend the bible by saying it has been altered by man.
The age of Humans/Earth to my understanding is ambiguous in the bible too. The number of years was calculated as an estimation of the number of kings, prophets (narcissists) and messengers (wankers) as they follow one generation after another.
I believe koran claims descendancy from the same line of prophet kings all the way up until abraham. So the same calculation will apply.