I really think they are aiming for those Android devices mentioned at the hardware adaption wiki. Nexus 7 and 4, Samsung S3. Those are the most common devices amongst the people who have accustomed for changing roms, and they are eager to try something new. Every android hacker in XDA-developers has one of those devices (and plenty of others too in the drawer so they can spare one).

This means that they'll have a chance grow the Sailfish OS user base exponentially in a single night. This is brick and mortar of their business no matter what they are planning to do in the future.

Currently there is a gap in the device ecosystem that was left by HTC. What happened to HTC was that they lost their wind as a hacker device manufacturer. They did it plain stupidity by locking their bootloaders, if only for a brief time.
They didn't realize what they had in their hands: Number 1 status amongst the Android community of forerunners that eagerly give their views and opinions to anyone who is interested about getting a new phone. Now HTC has to compete with the big players without any special advantage, and is losing it badly.