Honestly? Motivations aside, and granted that they would have been much better served making this decisions months ago, this isn't really a bad thing for this particular movie. This summer season is absolutely packed to the brim with competition for the demographics GI Joe is marketed towards. And frankly, the first movie wasn't nearly critically and commercially successful enough that given the choice, people are going to spend their money on tickets for it rather than DARK KNIGHT RISES, SPIDERMAN, PROMETHEUS, MEN IN BLACK, the new BOURNE movie, the EXPENDABLES sequel, even BRAVE and SNOW WHITE AND THE HUNTSMAN or just going to see AVENGERS again. I mean, a lot of people I know are consciously budgeting their summer movie watching this year, there's so many choices.
The first GI Joe movie was fun. I enjoyed it, but it wasn't amazing cinema or anything. The people who enjoyed it enough that they were chomping at the bit to see the sequel in a month aren't going to be put off enough by the move that they're not going to go see it when it finally releases in March. The people who are hyper-critical about moves like this and will view it as proof its a bad movie probably were unlikely to go see it anyway. And the vast majority of people who don't care either way and just want a fun popcorn blockbuster will have a lot less options and more disposable income to part with when March comes around.