Theres a thread for this in General Sports..
I posted this below on March 2nd, when Trump started his tiff with Iran. But apparently according to the FIFA rules (reported on BBC), they can assign any team they wish as a replacement. USA v Russia final? as boycott plays a straight bat and no one turns up.
Iran likely to be replaced by Iraq, with UAE taking their place and to play Bolivia in the play offs according to some.
But, I wouldn’t put it past the powers that be to include Russia playing under a neutral Asian flag as a direct replacement for Iran and leaving the play offs as is.