The current Vivofit descriptions suggest that it is coming:
Keep Moving
When you're ready to take the next steps toward better health, vivofit has additional features to keep you motivated. Use a heart rate monitor with vivofit to record your heart rate data and get more accurate calorie burn information for any fitness activity, such as a run or a session at the gym. For detailed calorie tracking, you can create an account at MyFitnessPal and link it to your Garmin Connect account. This allows you to compare calories consumed to your total calories burned, which vivofit records throughout the day. Also at Garmin Connect, you can join online challenges with other vivofit users or start your own competition with friends to compete for virtual badges and bragging rights.
Would be great to get some timeframes on this, but I suspect that at its earliest it will not be out before Vivofit is released which is due 1st Quarter which as we all know really means the last day of Quarter 1.
Still looks positive.
Just received my shipping notice from REI, should have the Vivofit by Friday. So they are shipping in the US now, the question is will Garmin follow thru on what you said above for MFP.