How much upside could this juggernaut stock possibly have left?With shares of Eli Lilly (LLY 2.68%) temporarily jumping more than 10% on Aug. 8 following its earnings report for the second quarter, it's easy to conclude that the company's spate of good performance is destined to continue forever.But is there evidence to actually support that assertion, or is it a mirage masking an investment that's sure to burn investors who buy in right now? There's at least one argument in favor of each of those perspecti ...