Depending on how you formatted the disk the old wallet.dat may still be recoverable. Most modern OS installations do a quick format which erases the meta data for files located on the disk but not the actual files. This however allows for the Newer OS to overwrite thee older files even though you have no clue they're even there.
If these older files have not been overwritten then yes the data can still be extracted using numerous professional/enterprise data recovery tools.
If however the format method you used was something along the lines of kill disk then yes you're most likely screwed lol... Back in the day when format actually zero'd out the disk platters it was slow as crap however since drives are no longer less then 10GB most OS'es will just do a quick format unless you want to wait hours to install an OS.
G'Luck though