Well.. for WoTC, it's about more than just selling books for the sake of selling books. At the root, 4E did not sell anywhere near as many books as was expected since a large group of people could not get over the changes to the game. There was a large focus on making the rules simple enough for new people to be able to pick it up and play fairly quickly(which I think they mostly succeeded at), but that came at the cost of many older customers who "knew" the old way and did not want to play a simpler game. Many of their customers ended up moving to other game systems. This feed into point two, where not enough customers subscribed to their digital initiative. There are many reasons for this. There were issues with "computer game" licenses which was "one" reason why the gametable was not originally released in the expected time frame. This further alienated some customers who stopped their spending which reduced R&D budget, which caused people to stop spending, which reduced R&D budget, etc. Add into this the global recession and well, money became quite tight, so promises made could not be kept.

I currently play a 4E game and also run one(on a monthly rotating DM schedule, so I GM about 5-6 times a year and play about the same). When 4E originally came out, I loved it's simplicity over 3.5(also note, we were playing with custom Magic rules using the Elements of Magic rules from EN Publishing) and the fix of things that were just horribly wrong with previous versions. Now, after several years, I am feeling a bit constrained and thinking of something else for the campaign I GM, namely thinking of switching the characters over to Savage Worlds instead. Pathfinder would not work for our group since half of the players are casual players and just don't have the time or desire to become experts on their character(which is where 4E "mostly" shines IMHO) and the game in general. For example, when I am playing, my turn rarely takes more than 20-30 seconds since I know my character so well(it also helps that I am a leader so heal and buff are what I do and it's fairly easy to see who needs health or might need extra hitting power or defenses for that coming round). But if I have to also play someone elses character(as I did this last session), it probably took me 5 times that since I was trying to both determine what that character can do at the same time as paying attention to what was happening on the battlemat. We were fighting a creature that could turn invisible and he was in a zone(debuff's him and opposes penalties to whom he can attack), so I had to keep watch to make sure that he stayed in the zone by using powers that would slow, immobilize, or blind him(while other people's powers would also do one or more of those same effects for a short duration.