From the middle of next month, to the end of May, OnePlus will build up enough inventory to cover all of the early invitations sent out to consumers who want to buy the phone. In early June, OnePlus will start to produce the larger capacity 64GB Sandstone Black model of its phone. By later in June, anyone who wants to buy a OnePlus One will be able to procure an invitation.
According to OnePlus, the public is really leaning toward the 64GB Sandstone Black model by a wide margin, over the 16GB Silk White variant. We don't think that OnePlus is artificially boosting the demand for its phone by keeping production low. Rather, the company says it is a matter of more people wanting the device than OnePlus had been anticipating.
While not everyone who wants a OnePlus One is going to be able to buy one immediately, this demand is a good sign of things to come, once supply can be ratcheted up to better meet this demand.
source: OnePlus via AndroidandMe