Its hard to say at this point, Silva will be making do till he gets in the players he wants, ideally he will want this :
GK
RB - CB - CB - LB
DM
CM - CM
RW -- ST -- LW
The problem I see is that we simply dont have the players to fit that system, certainly not in midfield, Gana is a good DM, but hes a chaser, not a sitter, Morgan is a good DM, when motivated, but hes a sitter and doesnt chase, thus Silva is forced to play them both. ideally he has a player who can sit, but with a good passing range and of course 2 number 8s in midfield. So that leaves us with the 4-2-3-1 that we will probably mostly play.
When Gomes is fit I will be interested to see if he gives the 4-3-3 a go, but suspect it will be Gana or Morgan playing the 6 with Iceland and Gomes as the 8.