By Apple's return policy, if they set a permanent price reduction within 14 days of the original purchase of a device, they will cut you a check for the difference. Since they not only reduced the price, but also improved the processor of the original watch, you could ask if they would do an exchange as well or possible widen the difference.
Quoted from Apple's official sales policy:
"Should Apple reduce its price on any Apple-branded product within 14 calendar days from the date you receive your product, feel free to visit an Apple Retail Store or contact the Apple Contact Center at 1-800-676-2775 to request a refund or credit of the difference between the price you were charged and the current selling price. To receive the refund or credit you must contact Apple within 14 calendar days of the price change. Please note that this excludes limited-time price reductions, such as those that occur during special sales events, such as Black Friday or Cyber Monday.
Hope this helps!