Shopdressonline has the Oceano Magnolia, and their 20% off "treesje20" code should still be valid, though I'm not sure when it expires. Aster Alice also still has their 20% off "welcome" code that should be valid on pre-orders and on Treesje until the end of July. (Email their CS about it if you encounter any issues, they allowed it for me.) You can use AC points too, if you have any, which makes it a better deal. I know LB is taking pre-orders on the Oceano and Bordeaux Magnolias too, but I don't think they have any valid codes right now. As for other boutiques, not sure if there are codes!
As for whether or not you ought to go for it, it's definitely up to you: how badly you want the bag and your personal willingness to pay. If you really want one very badly and don't mind paying full price for it, it may in fact be a good idea to take advantage of the remaining codes right now (at SDO and AA) to get a slightly better deal at 20% off. OTOH, if your personal willingness to pay just isn't that high, and you may come to regret paying that much for the bag right now, it may be a good idea to wait and see if better deals come along. (This is also where an "if it's meant to be, it'll be" attitude towards bag-buying comes in handy!
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Oh, another thing you may want to consider is checking the current remaining quantities at various stores. (You can usually do this by adding the item to your cart and then increasing the quantities until you get an error message.) Even for pre-orders, it should still give you an idea of how many bags a store will have left once the bag is actually in stock, and hence whether or not the remaining stock may go quickly. This may help you with determining how badly you want the bag, I guess!
HTH!