Amazon will be a distant but healthy #2
Amazon's pads will do better than any other Android pad. Because only Amazon has the breadth and depth to support their pads. They have years of experience building Kindles, they have years of experience delivering digital and physical goods to customers, and they have hundreds of millions of account holders and credit card info.
But it's the intangibles that will really help their pad(s). Amazon has enormous mindshare and enormous brand equity. It's one of the world's most-trusted brands, and that will provide a significant "halo" effect for their pad(s).
Compare all that against Motorola. And HP. And RIM. Motorola has deep experience building phones, but are just an OEM. No customer-facing ecosystem like iTunes and App Store or Amazon's online store. Same with HP, except that HP builds pee cees and printers, which may or may not help them sell pads. (And yes, I know how great webOS is. But a great OS alone doth not a successful pad make.)
RIM gambled that they could coast in the smartphone arena, then leverage their deeply entrenched BlackBerry business customers to sell PlayBooks. It didn't work. And it turns out that the reason why PlayBook doesn't have built-in email is baked into the BlackBerry BES mail server. A user gets a digital identity (PIN) and that identity is assigned to a single device. You can't have both a BlackBerry phone and a PlayBook pad with the same PIN. Thus, the PlayBook can't have a BES email app. Fatal "vision problem" there, eh hoser?
iOS 5's improved messaging is a headshot to that old staggering zombie. And there won't be any "business tablet" market (hear that, Dell? Ballmer?). Microsoft proved that by failing to make a dent in anything after 10 years of waving UMPCs and "slates" around at CES keynotes.
So that leaves Amazon, with its massive customer-facing infrastructure, vast experience, and all-important mindshare. They seem to be stuck with Android for the moment, but despite that they have the best chance to win the battle for 2nd place.