ICv2's numbers for March:

93 --- 43.16 --- BLACK PANTHER #35 --- 21,332

That's an 8.8% drop off from #34, and the seventh consecutive month that the book has lost more than 8%. It's simply not leveling off, and like Paul O'Brien said last month, it's well on track to drop below 20K next month.

Now the Aaron SI arc is guaranteed to spike sales, but that's just a stopgap, like every other crossover has been. So my advice to Marvel is:

Don't cancel the book yet. Don't look at these numbers and assume that the public simply doesn't want a BP title. Before you take that route, replace the writer. At least experiment and see if another [non-crossover] author can hold onto readers in a way that Hudlin's writing obviously doesn't. I suspect that's what you're doing with Aaron, but if you're going to extend the series this long a lifeline with the same writer, you should at least try extending it without him.