- Greece, Bulgaria, and Yugoslavia stay neutral
- All the German Troops dedicated to fighting in the Balkans and Africa go to the USSR
- Probably a Axis victory scenario
The Germans really did not have all that many troops in the theatre, and moved most of those to the Eastern Front after Greece's capitulation. They conducted the Dodecanese Campaign on a shoestring budget.
Africa was a drop in the bucket in terms of German resources expended.
Now, this was different for the Italians, who really did have a lot of troops in Africa and the Balkans. The extent to which more Italian troops on the Eastern front would have made a difference is debatable, due to the troop quality involved outside of the Bersaglieri and some of the well equipped Armored units. It wouldn't hurt, but it might not be all that decisive. However, Italy was in World War II for its own territorial ambitions around the Mediterranean. I don't think the prospect of a Pan European war against Bolshevism held enough appeal for them to send a huge part of their army east if they weren't getting any land out of it.
Mussolini's decision to go against Greece was not threat assessment. They had territorial claims against each other pertaining to Italy's post WW1 territorial gains, but they were also kind of just in the way.