With this week's release of Verizon Wireless' Droid phone comes the first real test of the potential for fragmentation with Android.
The Droid will be the first phone to run Android 2.0. After it goes on sale Friday, there will be Android phones on the market running three different versions of the OS.
But operators and hardware manufacturers currently selling Android phones are coy about whether their devices will be upgraded to the new OS. If some phones continue to run old versions, issues could arise with application compatibility across the different OS versions.
Motorola, whose Cliq runs Android version 1.5, would not specifically say if users of that phone would be offered the 2.0 upgrade. "Cliq with Motoblur can be upgraded over-the-air and will evolve to support how people's needs change.
However, Motorola hasn't announced any updates at this time," a representative with Motorola's public relations firm said.
Google gave an equally vague answer to questions about which phones might be upgraded and if any of them had hardware limitations that might prevent an upgrade.
"Because Android is open source, all software updates we release are available for carriers and handset makers to take and update their current or future Android-powered devices," Katie Watson, a Google spokeswoman said via e-mail.
She also pointed out that the updated OS hasn't been released so no devices can be updated yet.
T-Mobile said it is coordinating with Google to deliver Android 2.0, but it did not address specific questions about which Android phones it plans to update.
Samsung declined to comment about whether the Moment will be upgraded to Android 2.0. Most Android phones, except the Cliq, run version 1.6.
Hardware limitations could decide which phones get the update, said Carl Howe, an analyst with Yankee Group. "As systems get upgraded, they tend to want more memory," he said.
The HTC G1, the first Android phone on the market, has 192MB of RAM and 256MB of Flash ROM. Most of the other phones, including the MyTouch, Cliq and Droid, have 512MB Flash ROM, Howe said. Most, except for the MyTouch 3G, have 256MB or 288MB of RAM, he said.
Howe believes that the G1 will be upgradeable to Android 2.0 and pointed to an online report showing a developer who has ported the OS -- based only on the SDK (software developer's kit), not an official release -- to the G1.
"It will boot and run apps, the only question is, will you be happy with it," Howe said.
He suspects that the G1 will get the update as long as the user experience is good. "If I were [T-Mobile], I'd be testing it and seeing what the experience is like," he said.
Another analyst wondered about the effect custom user interfaces might have on the upgrade process.
"If you're selling a phone like the Hero where there was work done by HTC, it's not clear if you can upgrade the OS without also upgrading HTC Sense on top of it," said Avi Greengart, an analyst with Current Analysis.
HTC built the Sense user interface on top of Android and it runs on the Hero, a phone sold by Sprint. Motorola similarly built an application called Motoblur used by the Cliq.
Because those user interfaces might have to be updated along with upgrades of the OSes, Greengart wonders if the phones with the "vanilla software," meaning the OS without any added enhancements, will get updates faster.
Developers of the custom user interfaces may have to update their software, after the OS comes out, and would likely push the two updates out together, Howe said.
Until now, there have been few Android phones on the market so the differences between them didn't have much of an effect on end users. But as more and more phones hit the market, their differences become more apparent. They have different screen sizes and resolutions and different hardware components like trackballs.
In addition, Android 2.0 supports multitouch, even though Verizon's Droid doesn't use it.
If developers write applications that "obey all the rules and have no undocumented features and they're careful, it will work fine," Howe said. "But that's a lot of caveats. Programmers have been known to take shortcuts."
That means there is a chance that some applications in the Android Market, which is shared across all phones, may not work well on some devices.
"This is the first go around as to whether it's an issue. If there's a big flap about it, people will scramble and try to make things better," Howe said.
"It's certainly dangerous. The great thing about Android is this is a boon for handset manufacturers because they have ultimate flexibility. But the downside is, as somebody innovates, the platforms tend to diverge and you have to worry about application compatibility," he said.
The potential issue highlights the benefits to Apple's strategy with the iPhone.
"It's one of Apple's great advantages," Howe said. "There's one screen size and one interaction mode. You write once and it runs pretty much on everything. That's not true on Android."