The forum merger would not bother me EXCEPT that D&D Next/D&D 5E needs to stay in its own forum.
My reasoning is that D&D Next forum traffic will flood any combined D&D forum because everyone will still be trying to learn the new rules, putting up character builds for peer review, changing and manipulating rules they have quickly decided they dislike, and so on.
All previous editions of D&D and Pathfinder (yes, even 4E) have already gone through that opening phase of "post-release playtest". Everyone that still likes Pathfinder or 4E has figured out 99% of the game already, figured out all the house rules that will make their homebrew campaign like they want it to, and all the kinks and loopholes of the game system have been fixed, embraced, or retconned, and its now mainly the players who have just now gotten around to discovering or warming up to Pathfinder, and those who just enjoy endlessly tweaking rules like myself, that come up with new and different ways to reshape the game system or write new content for it.
D&D Next (and any other brand-new game system) should have its own forum. If you must merge, only merge forums for the game systems that have been around for awhile.