Hi,
The newer MacBook models are a bit better than the older models, but it isn't a big deal. It isn't like the difference between night and day. You might as well be pleased with the MacBook you have - it is a great machine.
I'd recommend not upgrading to the newer model. You'll lose money selling the older model and you'll pay a premium for the newer MacBook because it is just released.
Now you know the drill - Apple usually has new models approximately every May. You can tell new models are on the way because on-line retailers start to cut prices and/or offer free accessories so they can empty inventories of the older models.
The Apple store employees were being disingenuous telling you they had no idea new models were on the way. Of course they did, or at least it wouldn't be rocket science to for them to posit a pretty good guess. Keeping the impending release of new models secret to prevent decapitating sales of existing models may be, "good business," but as you know personally, isn't good customer relations.
A more customer-friendly attitude would be to offer modest discounts on older models while keeping brand new models at list price. If you're like me. you'd take the old model at a discount while the gadget freaks could pay full list for the newest product. That way, nobody feels bad.
Too bad that Sam's Club doesn't sell a full line of Apple products. A few years ago, I bought a Samsung monitor at Sam's. They cut the price $50 a month later. I took my receipt and they gave me the $50 plus tax back - no arguing or balking. Now that's service! I've gone back to Sam's for other purchases as a result. My guess is that you'll always pay full list at an Apple store - but you do get some perceived benefit of hand-holding and advice while you shop. If you know what you want, on-line sellers will save you money, but you'll forgo concierge service.
Bill