Could ketosis be therapeutic for ADHD based on the neuro-energetic theory of attention? I'm a complete neuroscience novice so please bear with me.

One of the more interesting theories of the etiology of ADHD that I've read posits that the disorder may be one of neuroenergetics - the result of insufficient and variable neuronal energy production due to insufficient "formation and supply of lactate" in astrocytes. As the theory goes, this impairs immediate response to cognitive demands due to a lack of sufficient ATP for "rapidly firing neurons," and also affects development of the brain by impairing myelination on longer time scales. Abstract here: http://www.ncbi.nlm.nih.gov/m/pubmed/16925830/

I'm quite interested in how ketosis can be therapeutic for neurological/cognitive issues in general, and how it might ameliorate ADHD symptoms in particular - there appears to be some experimental evidence (at least in rat models) that it might do the latter. There also appears to be experimental evidence that ketosis increases levels of lactate in the brain: http://www.ncbi.nlm.nih.gov/m/pubmed/11043913/

My question: if the theory proposed in the first link above is correct, would it be reasonable to think that a ketogenic diet might eliminate ADHD symptoms by addressing the lactate supply issue? Obviously the effects of years of impaired myelination would still be present, but could ketosis resolve the more immediate energy-supply issue and also possibly improve myelination going forward?
Whether or not there is truth to this theory, a ketogenic diet cannot 'eliminate ADHD symptoms'. ADHD is an impairment of executive functioning. Executive dysfunction is thought to be linked to a deficit in dopamine, as well as functional frontal lobe pathology. (1) There are certainly other theories as to what causes the disorder, and they are likely a byproduct of how broad a net the traditional ADHD 'symptoms list' seems to cast.

There is no doubt that lactate is important. Recent evidence may suggest that lactate is preferentially metabolized over glucose by neurons in the brain. (2) However, while low lactate levels might produce behavioral effects that imitate those of ADHD, there is no evidence to suggest that the disorder itself can be traced to lactate levels in the brain. One way that we can observe this is by measuring executive functioning ability and lactate levels in humans as the result of acute exercise, since exercise is observed to raise lactate levels. This study shows that:


  ...While acute exercise improved all aspects of executive functions in those without ADHD, acute exercise only improved inhibitory performance for those with ADHD.


Thus, it does not look like the cure you are looking for is found in ketosis, assuming that it is the lactate you are monitoring (and also assuming that a ketogenoc diet does not raise lactate levels by a hyperincreased amount relative to that generated through rigorous exercise). Furthermore, the Wikipedia page for ketosis cites several sources that suggest that a ketogenic diet may be unhealthy, and even fatal if done improperly (4). But that last bit exceeds the scope of your question, so I'll leave you to look into that if you so desire.

EDIT: Forgot to tackle the myelination issue, which seems to be a big part of your question, as well. Decreased myelination appears to lend itself toward addictive behaviors, and may worsen existing disorders through psychopathological means, but does not seem to cause the disorders themselves. An increase in myelination may help regulate symptoms, but cannot cure the sufferer of the disorder or eliminate the symptoms entirely, which seems to be what you are asking about. (5) 
(6) A well-balanced diet that supports the strengthening of myelin (i.e. Omega 3) is often a method of regulation for ADHD sufferers, but is not the rule.