While I hope Jolla (or some partner) will also sell flashed phones directly (that could help adoption) I think it's pretty likely it will be possible to also flash you own device. It would be pretty stupid not make this possible, excluding a large number of people - current Xperia X owners and people who could get the device more easily through normal channels (remember all the restrictions for shipping of previous Jolla devices). Especially for something that's being called a community device.

Of course in any case an official clarification would be welcome!