There has been no official announcement from Marussia yet but the FIA entry list for the Russian GP as published at 4.35pm today features Alex Rossi in car number 42.
Marussia has built up its spare chassis and the car is available for the American to make his debut. However, the team will make a final decision on Friday morning on whether or not to actually run the car this weekend.
Rossi, who ran in FP1 in Spa, took part in the team’s track walk earlier today.
Giving Rossi his chance would clearly give the whole team something positive on which to focus at what is obviously a difficult time for all concerned.
Adam Cooper's F1 Blog 
Not a Rossi fan Adam but agree completely with your last. It would be extremely positive all around, hope it comes about.