I will give you a full report on my Martin J-15 in 2088.
In the mean time I can tell you that there was a noticeable opening up of that guitar after about one year. That kind of change is something I've observed in every new guitar that I've ever owned regardless of the type of wood involved. I suspect it may be more of a general construction settling process rather than 'opening up' of the top alone. Since that time I haven't noticed any change.