Some comments here are a LOT of BS. That is forgivable since many of Tom's readers don't seem to know much about mobile SoCs. Let's clarify some things.
1) Intel's new SoCs kick a lot of ass (just read some Notebookcheck reviews of devices with them) and are used in many new tablets and phones, especially Lenovo and Asus. Intel doesn't need ARM, it just needs to improve x86 more like it's already doing and ARM will squeal. A few years ago people were saying that Intel won't be able to release chips that can compete with ARM on power efficiency and performance - right in your face with Bay Trail. What people don't get is that besides having tons of money, Intel has some of the brightest minds in the world working for them. And beating ARM is just a challenge for them, one that I'm confident they'll win. Just wait for Broadwell-Y and Cherry Trail. At some point current ARM makers will go bankrupt unless they're smart like nVIDIA with its K1 (especially Denver version).
BTW:
The IGPs in Intel's current SoCs are still horrible jokes though and Intel will not have anything worth writing about in that department until late-2015.
Nonsense. Their current Atoms use scaled-down Ivy Bridge GPU that performs a bit behind Adreno 320 and their new Moorefield Atoms will use PowerVR G6400 (dual core models) and G6430 (quad core models). That's the same one as in Apple A7 chip in iPhone 5S. Moorefield is coming out in Q4 this year.
They (Intel's management) better not hear of this. They'll probably engineer buying out ARM itself.
And if ARM poses a real threat, they will. People tend to forget this too.
x86/64 will never be able to compete in the mobile space. The architecture has become so large and complicated that it can be made to run at the efficiency of ARMs architecture. Most of the power in big x86/64 systems comes from the fact that compilers and code have been optimized to take as much advantage as possible. The problem is the rules aren't the same for the mobile space and the same techniques used to give killer performance at the high end (massively superscalar, complex cache systems, etc) hurt performance for smaller devices. Atom is to ARM as AMD is to Intel, the performance is subpar but people use it because they can get it cheap. Intel can get there but their attempts seem half-hearted at best.
... right. So you are saying that code and compiler optimization is bad. Are you an Android developer by chance?

But seriously, just look at what you wrote here. How is ARM different from x86 in this regard? The most powerful ARM chips are those with most cores, highest clock and biggest caches. And THAT is how x86 gets most of its power, by having much more headroom to operate in, although of course optimization counts. In fact, the ONLY way to make any architecture powerful is optimizing applications for it, and that's what ARM has to count on the most - and so does x86. Intel's contributions to Linux kernel aren't just for fun, you know, they want their Atoms to work under Android properly. And in case you haven't noticed, unlike AMD, Intel doesn't simply try to stuff "more of everything" into their chips anymore. They've realized that modern x86 processors are more than enough for most applications and are now heavily focused on power efficiency, integrated graphics and heat management. To say that Intel's attempts are "half-hearted at best" is blind. They simply chose to first secure (read: crush the competition) the market sector they make most profit from (laptop and desktop) and only then dive into something they haven't touched before (mobile). I'd say that's a sound strategy. You don't leave the house without making sure you lock the doors first.
Intel has been trying to respond to ARM since it brought out its first Atom chips in 2008, back in the Netbook era. Remember Intel trumpeting its “Full Internet Experience” slogan? They said they were two years ahead of ARM at the time. Now they’re no longer quite as complacent.
First Atoms failed because of poor quality of the boards they came on (had to throw away about twenty of them at work in the last two years) in case of desktops and bad form-factor in case of laptops, combined with rapid increase in hardware requirements that Windows Vista and 7 brought (primarily RAM, those damn chips always came in devices only with 1-2 GB of RAM). Windows XP worked fine on my Asus Eee PCs, but I got rid of them both because they were too small and eventually, too slow. Rome wasn't built in a day, first Atoms were a good start and Intel has learned well. They are STILL ahead of ARM, in fact even more than ever before, because there are now actual mobile devices that use Intel chips, a lot of devices. MS got tired of Windows RT and asked Intel to make chips to run x86 Windows 8 on tablets, Intel delivered

Deal with it!
2) Mediatek is a steaming pile of garbage. Their chips might cost less than what customers perceive as Qualcomm equivalents, but perform worse, heat up more, consume more energy and have worse graphics. Moreover, they're buggy, search for "Mediatek SMS attack". Just messaging an = sign to someone with Mediatek based phone will cause it to reboot. MOREOVER, that <expletive> company refuses to release source code necessary for 3rd party ROMs like Cyanogenmod to be made for devices with their chips. It's despicable, because most stock ROMs - even pure Android, as I found out after buying a Moto G (can't even change Quick Tiles order and contents, what the heck) - are garbage and most companies abandon their devices after 1-2 years. Samsung refused to release KitKat for S3 and S3 Mini (except LTE version) because TouchWiz UI needs more than 1 GB RAM to run on KitKat. FYI: pure KitKat needs 512 MB. I'm running it on my Galaxy S1 (thanks, Cyanogenmod team) and it's smooth and stable. The only hangups I get are because of the CPU, but that's to be expected. On my GT-P6200 tablet with a stronger dual-core CPU that already doesn't happen.
TL;DR - Intel laughs at your underestimation of its potential and misinformed opinions; compared to Qualcomm, Mediatek chips run hotter, consume more power, are buggy and they won't release source code.