It’s the first day of fall in the U.S. and already the forecast is turning gloomy on whether the current batch of Android tablets can overcome Apple’s lead. Amazon, perhaps with the best chance to rival the iPad, may have already stumbled by putting up a 7-inch device against Apple’s larger alternative, industry experts warned Friday.

“Amazon may run a risk by releasing a 7-inch tablet when 10-inch models have mostly outperformed 7-inch competition over the past six months,” industry publication DigiTimes reports, citing unnamed suppliers. The online bookseller is expected to unveil a Kindle Tablet during the fourth quarter of 2011. The Seattle-based company reportedly wants to ship 4 million tablets this year, however suppliers “remain skeptical” whether that goal can be met.

Although any tablet from the company will likely benefit from the brand recognition and distribution infrastructure Amazon already has in place, the company may not be able to replicate its success in the e-book market. The device will need to compete with lower-priced devices, such as the $249 Nook Kindle and the $199 IdeaPad A1, according to the publication.

Greater concerns surround the general market for Android-based tablets. Industry insiders are “turning pessimistic” about the chances of the current crop of Android devices chipping away at Apple’s lead. Hardware sources tell DigiTimes that non-Apple tablets may have to wait until after the version of the Google software codenamed “Ice Cream Sandwich” or Microsoft’s Windows 8 appears.

Meanwhile, other industry sources predict tablet demand will fall “much like the bottom fell out on the netbook market.” In a bit of wistful nostalgia, the unnamed experts believe traditional notebook sales will return as consumers tire of tablets.