Mr. Tb and I are flying to Europe on M fares with mileage upgrades to B/E. At the time of purchase, we had plenty of time to make our ATL connection, but, due to Delta's (3) changes to our itinerary, the connection time has been reduced to a bare minimum (1 hour 20 minutes).

Fortunately there are a couple of later flights we might use if, due to weather or mechanical conditions, we miss our connection. Unfortunately, there's no guarantee that there will be seats available in B/E for our upgrades.

My question is: if we miss the connection and cannot be upgraded, what, if any, adjustments/compensation should I expect from Delta? Of course, I expect they'll redeposit our upgrade miles, but I purchased the M fares solely in order to upgrade. Should I expect any compensation for the difference between the M fares and deep-discounted fares? (I bought the tickets 6 months in advance when there were plenty of Q fares available.)