Ok that's what I thought. I don't remember exactly which version the wallet file was from, but it was probably generated in 2013, but used last before now in 2017. So that probably means a new keypool was generated for  the new address given that it was in the new format? I also noticed that the "new" wallet file had a different size than the old. I guess I'll have to wait and see...

Seems like there are two different answers here, hopefully the first answer is right.

How would I generate the new address from the old wallet file when I import it? Would the new address be generated from the old wallet's private keys?

Hi,

I have an old wallet.dat file that I was checking and found that it was an old format, and so had to download the full core client. Having downloaded the blockchain I then transferred a copy of the old wallet.dat file by overwriting the default one. Then I generated a new address and sent some funds to it.

The plan was to back-up this file, but as I did so I had a drive crash and somehow lost the file. I have a copy of the old wallet.dat file still.

Unfortunatly, I won't be able to get a copy of that file before Monday.

Have I lost the bitcoin in the new address or is there a way to recover the funds from that last transaction?