The practices are working on the schemes - which have a combined value of £500 million - for developers Brunswick Developments and Explore Living.
The focal point of the development is Wilkinson Eyre's £250 million Roaring Forties skyscraper for Brunswick. The 40-storey tower, which will be built 'out-at-sea', has been granted planning permission.
Allies and Morrison's scheme is still waiting for approval, and the new designs are expected to be unveiled later today.
The £320 million plan underwent extensive design changes after Explore Living gave in to residents' concerns.
Previously a 32-storey design, the scheme now has three towers of nine, 14, and 17 storeys, and a 26-storey tower has been replaced with four pavilion-like buildings, each 10 storeys in height.
The marina project will provide Brighton with thousands of new homes, plus new amenities such as pubs, shops and restaurants.
The new plans will go on show to the public tomorrow.