Yesterday, the Good eReader site broke the news that Amazon was telling publishers that they should start submitting their books in ePub format. Previously, submissions to Amazon were generally in the mobi format, which was a carryover from Mobipocket. This is both great and not so great.

Amazon’s use of mobi (or, more specifically, AZW, which was Amazon’s proprietary version of mobi) was kind of like Apple’s use of AAC for iTunes. There were a couple of different formats vying for widespread adoption (Windows had their Windows Media Audio, WMA, format, for example), and while MP3 was most widely used, there seemed to be some hope that there was room for contest. Nowadays, pretty much everyone uses MP3. The digital reading situation is somewhat analogous, where the format equivalent to the MP3 is, arguably, ePub–every reading device besides Kindle recognizes the format, and most of the other formats are based on it.

If you want to use Barnes & Noble’s Pubit platform, chances are you submit an ePub for best results. The iBookstore is based on the ePub format. Sony Readers display ePub.

So Amazon’s the odd man out. But it’s a rather large man, considering it basically owns the ereader market.

But they’re adopting the ePub format is not the biggest change this week.

Earlier this week, Amazon’s CEO Jeff Bezos hinted that people should “Stay tuned” for news concerning an Amazon tablet.

This after a job listing that mentioned devices “like the Kindle.”

There’s a lot of speculation floating around. Most of it seems focused on the idea that Amazon is going to release an Android-based tablet.

I don’t think that’s speculation. I think it makes sense, and I think the “Stay tuned” is really just confirmation as we wait for Amazon to confirm the details.

Consider:

-Not long ago, Amazon implemented the Amazon App Store for Android. Which seems to have the full support of Google, and is well implemented. You go to Amazon, sign up, and suddenly you have an email with a link to download the App itself, which is basically Amazon’s version of the Android Marketplace.

-Also not long ago, Amazon implemented the Cloud player, with its cloud-based storage. Right around the time that Google announced its own cloud-based storage, and while Music Beta for Google is rolling out invites to its new service.

-Amazon has, for a long time, offered streaming video.

I can’t imagine Amazon isn’t working on a tablet. It makes sense, and I think it’ll use the Barnes & Noble model: a basic, dedicated e-reader device (because the Kindle itself has been ridiculously successful) to complement a Kindle Tab. I’m not sure that will be the name (probably not), but I have a feeling Amazon is going to introduce to the Kindle family a device with an LCD screen. It’ll be Android-based (probably with some Amazon skin on it), and it will have easy access to the Amazon App Store for Android, as well as cloud storage and video streaming.

I wouldn’t be surprised if there were an actual partnership with Google, considering its line of Nexus phones, but I’m not sure how that would play against the nook and nook Color (both of which run on Android). I’m not sure Google wants to play favorites, but then again, Google doesn’t yet have its own tablet. It’s got several companies using Android to implement their own tablets, but not one itself, not a tablet version of the Nexus. Which is a bit surprising, because it seems like Google is really pushing Honeycomb but yet letting Samsung and HTC and others skin over it.

Amazon has demonstrated its proficiency for hardware with the latest generation Kindle. It’s a dream of a device with a beautiful screen and terrific implementation overall. It’s thin but solid, and it feels great in terms of both texture and weight.

On the other hand, I’m not sure how Amazon’s cloud player would play against Music beta for Google, or how the app stores would complement each other. I don’t think that close a partnership is possible just yet. I just wouldn’t rule one out in the future.

I definitely think there will be a sub-$100 Kindle by the end of the year, though.

I also wonder if a new Android-based Kindle tablet would replace the Kindle DX. It would sort of make sense. It’s bigger than the regular Kindle but not hugely so, it’s due for a refresh (it’s still using the same layout as the old Kindle), and it’s hovering at around a price point I’d wager Amazon would prefer to stick approximately to. I’d actually peg closer to $300 simply because I’d expect they’d want to compete better with the nook Color at $249, but then again I think they’d also like to introduce something that will demonstrate how the nook Color is basically hobbled unless you root it, and overall not the premium experience Amazon is going to aim a tablet at.

We’ll see, I guess. “Stay tuned,” as Bezos said. In the meantime, speculation sure is fun.