In untreated addison's disease, would basic metabloic panel always be abnormal? low sodium, increased k?

Never say always: As addison's disease (primary adrenal failure) progresses, there will most likely be obvious hyponatremia and hyperkalemia. But these changes may be subtle in the early stages, and the diagnosis can be be more properly suspected with a presentation of prolonged nausea, vomiting, anorexia, weight loss, low blood pressure, and weakness.

Not necessarily: Early on in the course electrolytes may be normal, though may become abnormal during physiological stress. With adrenal insufficiency, there may be normal baseline cortisol on board, but with an illness, surgery, accident, etc. That degree of stress may tip an undiagnosed patient over the edge into an adrenal crisis.