Back in October Microsoft announced a temporary price cut on the Xbox One. From November 2nd, 2014 until January 3rd, 2015, the cost of the Xbox One dropped by $50.
Honestly I thought that the temporary nature of this offer was just a marketing gimmick and that the price would stay at $349, but I was wrong. Over on Xbox Wire Microsoft posted a reminder that the offer ends this Saturday, January 3rd.
Various retailers have sweetened the deal further. For instance Amazon is selling the Xbox One Assassin's Creed Unity Bundle for $349 and throwing in $50 in Amazon credit to boot. Best Buy has the same kind of deal and Target goes even further by offering both a $50 gift card and $20 off a one year Xbox Live Gold subscription (the Xbox Live discount offers ends 1/31/2015 at 11:59 pm PT).
If you want a second Xbox One controller you'll want to shop at Toys R Us where any Xbox One purchase comes with an additional wireless controller.
Newegg has an offer that ends on January 2nd. They're throwing in a $40 gift card and a full year of Xbox Live Gold with the Assassin's Creed Unity bundle. That's close to $100 worth of bonus goodies.
I've noted any specific cut-off times listed on the various websites. The rest are just listed as "while supplies last" and generally speaking you can assume they all end on January 3rd at the latest. All the stores reserve the right to change/cancel these deals at any time.
If you're in the market for and Xbox One, order it now before these deals expire, or be prepared to wait a while for the price to drop again. I've spent a lot of time over the holidays playing Forza Horizon 2 (and its new Storm Island expansion) and Farcry 4. The Halo 5 multiplayer beta launched yesterday. Plenty of my friends are deep into Dragon Age: Inquisition.
The point is, you were smart and held out for a year after launch. Now the price has dropped, the OS has been greatly improved, the games are here, and these online retailers are willing to sweeten the deal quite a bit. If you're at all interested, now is probably the best time to buy the Xbox One, unless you're willing to wait until Holiday 2015.