I doubt Guinness would let them rebrew it and call it Guinness? And if Guinness did then surely they'd just give them the recipe from the archive? The pessimist in me sees a modern beer with modern ingredients coming, with an olde-worlde label ...
Guinness found on 162-year-old shipwreck inspires divers with ‘Project Jurassic Beer’
Divers aim to scientifically ‘rebrew’ old stout to ‘unlock a form of liquid time travel’
irishtimes.com