We know that when we see this kind of news without conditional, the fight is announced quickly in well 90% of cases. The World Cup having passed, I expect an announcement in the week or the next.
This tweet comes across as a verbal agreement. Unless contracts are signed, I assume the fight isn't happening.
Krassyuk is one of the most credible, straight-shooting, no-nonsense, no-shitty-attitude promoters in boxing ever. His track record of always telling the truth and explaining things in a transparent manner speaks for itself.