In June, Coral slashed the odds on Prince Harry and Meghan welcoming a sibling for Baby Sussex.
"We have been inundated over the last few days with bets on Harry and Meghan having a second baby in 2020,” spokesperson John Hill told The Mirror.
"And, as always with gambles of this kind, there is seldom smoke without fire."
However, Nicholl said the rumours may be premature and that the couple is focusing their attentions on baby Archie for now.
"They absolutely want siblings for Archie, so possibly we will have a pregnancy announcement -- a second pregnancy announcement for Meghan and Harry sometime next year -- but, for the moment, the focus is obviously on Archie," she continues.
The royal couple recently held a small and intimate christening for Archie, which took place on July 6 at Windsor Castle.
Nicholl noted how becoming parents has transformed Meghan and Harry.
"Their life has changed enormously.., this really has been a life-transforming event," she told Entertainment Tonight.
"Yes, they're royals, yes, they probably have more help than the rest of us, but this really has turned their world upside down for the better."