Considering Capello actually wants Gerrard and considering the other transfer targets such as Pasqual (another leftback?!) and already purchased Marchionni. Hypothetically Capello could be working on something such as the following for next season:
Buffon
Zambrotta Thuram? Cannavaro Pasqual?
Gerrard Emerson Vieira
Ibrahimovic Trezeguet Mutu
Though will Thuram still be our number one centreback next season?
Do we really need Pasqual? The guy has a great left-leg, but his transfer would really be unneassary. We already have plently of options for the left-back position. With Perez now gone, Madrid buying Ibrahimovic has become less likely. Capello will surely use Ibrahimovic for his plans...... I think Mutu will force his way into the line-up, one way or the other. Other options are Del Piero and Marchionni. I think Nedved will retire, or will take a more marginal role within the squad. Sadly, I think ,one of my favourites, Camoranesi will be the one to pay for new arrivees and will be sold the coming summer.
Though Capello might opt to continue with 4-4-2, which could result in something as the following, which looks a little odd honestly.:
Buffon
Zambrotta Thuram? Cannavaro Pasqual?
Marchionni Emerson Vieira Gerrard
Ibrahimovic Trezeguet
I don't think that formation would work out if played like a standard 4-4-2. Add to that I think the team and certain players( Del Piero and namely Mutu for next season) would benefit if Ibrahimovic actually were to be sold. Hopefully Camoranesi will be kept aboard as well.
All in all I think Gerrard's purchase would unbalance our formation. Even in a 4-3-3, where I think the midfield would lack a forward drive playing with so many central (defensive minded)midfielders.