Yesterday the Football Association (FA) announced it had shifted the prestigious event to the Millennium Stadium in Cardiff because it was not 100 per cent confident Wembley would be ready.
But Rod Sheard of HOK Sport - who has worked alongside Norman Foster on the scheme - said there was still 'a damned good chance' the stadium would be usable in three months' time.
He added: 'It is a bit of a shame Wembley will not be used for the FA Cup and I'm in no doubt during the year it will be used for some events.'
Sheard, however, said he understood the reason the FA had decided to move the final following statements made by Multiplex about the progress of the project.
Just last month the Australian developer admitted there was only a 70 per cent probability Wembley would be finished on schedule - odds the FA were unwilling to take a risk on.
Sheard said: 'The FA needed absolute certainty. You can't let the supporters down.
'The most important thing is that they get Wembley right and, come Christmas, when the stadium is fully opened, people will have forgotten about it all and the missed FA Cup final.'
It is thought the first event to be held at the newly opened 90,000-seat stadium will be a Bon Jovi concert in June.
Meanwhile, in the wake of the Wembley debacle, Multiplex is considering selling a further £200 million of UK property assets and could let go of its £700 million mixed-use scheme at Paddington Basin in West London.