The downgrade to Neutral suggests that JP Morgan sees limited upside potential or increased risk in SAIC's stock, which could lead to a neutral or slightly negative short-term impact on the stock price. However, the increase in the price target to $142 implies a belief in the company's solid fundamentals or future growth prospects, which could counterbalance the negative sentiment from the downgrade. The mixed signals may result in a neutral short-term impact as the market digests both pieces of information.