LFR actually allows Blizzard to spend more dev time on making raids. If they removed LFR right now, what % of the people who only do LFR would actually move to normal raiding? A very small % I would argue for.
If there was only normal and heroic raiding now, it would be such a small % of the playerbase that Blizzard wouldn't put much effort/dev time into making raids, they would spend it on other things that the other % of the playerbase was enjoying.
I would argue one of the reasons that in MoP so far we have - 16 bosses - 12 bosses + 1 for hc only - 14 bosses is because with LFR there is such a bigger % of the playerbase acutally doing raids which can allow them to make big tiers again and spend much dev time on them.