if bitcoin is still around and all, will the mining (calculation of the blockchain) be so difficult where one block could get as large as 100GB in file size?
The Bitcoin difficulty has not correlation with the block size.
What is put in place where bitcoin will not time out because the transactions are just to difficult to process and store?
The block size limit, which is currently 1 MB. The block size limit is a consensus rule and does not change due to mining difficulty.