The packaging for the Sunny and Blaize the dragon set seems to confirm what has been rumored . . . that Hasbro will continue Tell Your Tale (the 2D animated G5 series on Youtube) but discontinue 3D Make Your Mark after its current season is done.
I'm honestly really disappointed because even when MYM has mediocre episodes, the ponies are sooo cute with their Muppet-fuzzed faces and fluffy hooves. And the episodes have been getting better with each chapter. However, from what I heard Hasbro did product testing with each show, and the kids responded better to Tell Your Tale.
I don't know how Hasbro measures that, but a lot of MLP's audience does skew young (always has . . . I got my first MLP when I was 4) and for very young kids, yeah, a five minute comedy episode is probably easier to follow without getting distracted or scared. I think Habro should still keep MYM, though, to draw in older kids, who probably don't find TYT "cool" enough.
There are also rumors that there will still be some longer specials in the future, and I'm not sure if those will be 2D or 3D.