Re: thermal movement
Liquid Metal has elastic properties, so once bonded to the sapphire glass (the patent describes the process to make that happen ) it will not separate again.
Assuming it comes off as described, it would be an amazingly durable device. Scratchproof face, and likely impact resistant to normal drops from head height or less at most/all angles. Liquid Metal itself isn't scratchproof, but it is significantly more scratch resistant than the machined aluminum Apple currently uses. If they waterproof it as well, no one will need a case unless they want to bling it out.
Though I wonder, if the bezel is bonded to the glass, what will they use for the back side? If the back side was also sapphire and also bonded, it would be essentially impossible to open. Not that this is really a problem, since 99% of iPhone owners will have Apple service it anyway, but iFixit might have to add a zero to their "repairability" score range of 1-10 if that happens!