According the the official site's description, 'the Comic' is supposed to be new PokeSP content, old ones and also guest contributions. Namely, the will have the Red and Pika chapter, some PokeSP related stuff in colour (I guess it's like what they did with Wonderland previous, some full colour pages explaining previous arcs), some selected 'fan-favourite' PokeSP old chapters, some XY game news (so it's not manga only materials then I guess?), and also pages from Pokemon BW Good Partners. The way the worded the Good Partners content was a little fishy. They say it will feature its 'conclusion chapters', and I'm not sure if it refers to the last chapters which were already serialized, or they actually are continuing from where they left off to give a more fulfilling conclusion.
Anyway, the tone of the writers gives me hope that the release may not be a one-off publication as I thought, and it seems the formula they plan to use is New PokeSP chapters + old 'favourites' PokeSP chapters + guests materials.
What's interesting is that the writers are referring to this as a 'Mook', which is a Japanese term describing something between a 'M-agazine' and 'b-OOK', thus a MOOK. I guess that tells us the nature of how this publication will be.