Contact Expedia ASAP. Now. Don't loose any time and prepare yourself. Read attentively the purchase conditions and guarantees they offer. If you are not satisfied contact them ASAP and ask for an immediate answer on the questions you have, prior to the grounding, which might well happen soon.
If you can, ask for a change of carrier if at all possible. To go on the safe side, try to get a travel insurance, if in Switzerland, try Wincare. do all these things before it happens just to make sure. If the ticket is only valid on Alitalia, it might be that the alliance partners might not accept the ticket in case of grounding. Is your ticket issued GVA-FCO-GRU or otherwise?