Not wanting to be left behind and forgotten in the "who's first to 64-bit" battle, Intel has announced that new devices coming out with Bay Trail (Intel's tablet chip platform) sometime in 2014 will have 64-bit support enabled. Unlike ARM, Intel doesn't need a new ISA, because they were already using the same x86-x64 ISA of theirs, it's just that the 64-bit parts in the new Atom chips have been disabled, to lower costs.
Intel does this all the time with other features in their chips, too. For example, the Core i5 chips may support a certain feature, and it will be available in Core i3, too, but it will be disabled, so you'll never be able to use it. This decreases complexity somewhat for them, since they don't have to make very different chips for each price range, and therefore it reduces cost.
Intel decided not to release their new Atom chips with 64-bit support, so none of the current Bay Trail devices on the market will support 64-bit. From the looks of it, the first Merrifield (the actual Atom made for smartphones, since Bay Trail is too power-hungry/expensive for smartphones) smartphones won't be supporting 64-bit either. But Intel says that in Q1, 64-bit Bay Trail devices will be available, just not with Android, so that means we can expect 64-bit Bay Trail devices sometime close to mid 2014 or later.
The problem with that is that Bay Trail's successor, will arrive a few months after that, so if you really want to wait for an Intel 64-bit enabled tablet, then you're better off skipping Bay Trail altogether.
We'll also have to see what benefits or downsides Intel's "64-bit" platform will have compared to ARMv8, ARM's 64-bit platform. ARMv8 is a clean break from the past, and a well designed architecture, while x64 (or rather its true name, AMD64) was designed as an add-on on top of x86, so it's stuck with a lot of legacy stuff, which will continue to keep Intel chip prices higher than the ARM competition, even as they make them smaller, being one process node ahead (although next year we should also start seeing 20nm ARM chips, too).
Bay Trail has also failed to impress this year, as even though it's a tablet chip, it can barely beat last year's Exynos chips, or this year's smartphone chips, especially in the GPU department, where Atom always seems to be at least one generation behind the competition in terms of performance. We'll see if Bay Trail's successor will be any better, but if they maintain this "release the tablet chip first, then the smartphone chip 6 months later" schedule, it probably won't do any better.