> the energy return on energy invested goes down, so net energy availability drops

No? EROI going down is like margins going down–that doesn't mean profit stops growing, it just grows more slowly per unit of input.

Lower EROI on a much-larger energy base means we're producing more net new energy today than at any time in history. That would be expected to continue all the way to EROI being close to zero. Until EROI is negative, you wouldn't expect to see net energy availability drop. But we have no foreseeable place where that's the case given solar panels exist.