You are right in a way, from my point of view.
I guess that as much Asics there are as much the owners of the asics will have to sell bitcoins to cover their expenses and initial investments.
By now it seems like they are not selling all the BTCs they are mining because they don't need to, they are making 46% of profit at the moment (at least I read so in blockchain.info statistics). But once there are a lot of asics sold being the number of mined BTCs each month the same, they will have to sell more and more BTCs, or the price of BTCs has to go on rising. Let's see.
Seems like it's not a good idea to invest in all those Asic shares now ... Most of them will probably lost money at the end of the year, prolly overrated.
But people are going crazy about it, and it must be taken into account.