I don't like the trend either, I found that the couple of map packs I bought for BF2 went largely unplayed, but I couldn't pass up the opportunity to play an updated Sharqui Peninsula or Strike at Karkand. I just hope they aren't too boldly re-imagined.
BF3 shouldn't suffer too much with this particular DLC. So many people will be playing that the community should be able to support the haves and have-nots easily. To be fair I got so much playtime out of BF2 that giving them some extra cash for some maps I barely played doesn't hold any regrets for me.
Ideally though, I would have liked to see these retro maps included in the main game and used to market it that way, but I think what they're doing is very canny in a business sense. It's no wonder that the pre-orders are doing so well.