Yes. It means that to attack Bitcoin one must only make the reward higher to do so. And if the reward for supporting Bitcoin tends toward zero the cost of doing so is fairly minimal.
It's the margin that tends to zero, not the reward.
Your attack is self-correcting, manage to make the global hashrate drop, everyone's rig is suddenly more valuable.
Tell us all a bit more about the magic of hashrate adjustments and the lightning responses. /sarc
Hrm? Elaborate a bit on the practicalities of your cheap attack where one "must only make the reward higher" will you?
IIRC, some sha256 alt coins which use the same mechanism found it more practical to just re-distribute new binaries than to wait it out when faced with PoW attacks.
Luke-jr raped some altcoin once, that's a super cool story but that doesn't really relate to Bitcoin in any way other than being some lame anecdotal evidence for your nebulous argument.