Hmm What would I like to see. I would like to see the 3.x books updated and released in one single book ( 1 book of spells, 1 of base classes,1 of prestige, items , feats, etc). Being able to look in one book not 10 to find something would be nice. Psionics and epic of course but everyone is looking for those. Maybe a book of cultures for those looking to play in another setting (rules to convert to asian, arabian, african, etc all in one book). I want to have 1 core book that cover an entire category clearly and cleanly. A lot of the races/ Prestige classes released in 3.x could be combined to make a better playable class with selectable choices (example :dragon shaman and marshal are almost the same in terms of their auras. combine them to 1 class with a selectable path ala sorcerer). I feel this approace is better for the community because we would have the choice to include only those books that we will use.
As far as number a year 2-4 sounds good to me.
Just my thought.