The announcement should be coming out any day now. Your guesstimates are likely pretty close. Looks like a lot of other MLP's are paying on May 15th, so I'd bet on that date or right around there. I'd be guessing ex-div is April 28th at the earliest.
Today MMP's closing price was $33.13. The last 4 distributions totaled $2.062, which gives a yield of 6.2%. I bought shares/units in 2003 and my cost per unit is $18.49. In effect, my current yield (2.062/18.49) is 11%. The 79% rise in unit price has been welcome too. That is why I hold MMP.
Re to drew "Care to share your list of MLPs ?" I am only interested in Pipelines as I think they are most safe. I am a retired low risk investor, looking for income stream. I only have those pipelines 5 years or more on my list. The column after the ticker is a straight line trend line, best fit for distribution growth over the last 8 quarters.
The next down that list is TPP @ 1.2% growth, with one move in the last 8 quarters.
I own the top 6 on this list. I sold BPL to get one of the better players, I do not remember which. I sold TPP when I realized they had quit growing. I was late to the party in recognizing that and resolve to not let it happen again.
My style of investing is suited for my needs and personality, others should create their own. Just share my thoughts here.