Increased block size limit to 2mb - code?

[coinscashout]

I was just reading about the increased block size limit from 1mb to 2mb and that the code will be released in July and will hard-forked in july 2017.

Now technically I'm not very sound when it comes to mining bitcoins as I'm still learning. My question is does this mean the coding of how the header is hashed will change slightly and include more variables (eg timestamp, nonce, merkle root etc) or does this mean the transaction are just going to be upped to a limit of 2mb and the 2 rounds of 256 hash will remain the same?

Thanks